### Subtraction of a sum

Sometimes we need to subtract a sum of elements from another element.

Rule:

$aβ(b+c)=aβbβc$

- This is also true in algebraic expressions.

We can operate according to the rule: apply the subtraction sign to each of the elements included in the parentheses.

Likewise, we can act according to the order of mathematical operations starting with the parentheses - calculate the sum and only then subtract it.

**For example, in the exercise:**

$21-(7+2)=$

#### Option 1 - according to the rule:

We will subtract each element in the parentheses separately and it will give us:

$21-7-2=12$

#### Option 2 - according to the order of operations:

$21-9=12$

Click here for a more detailed explanation about subtracting a sum.

### Subtraction of a difference

It is valid when we need to subtract a difference of elements from another element.

Rule:

$aβ(b-c)=a-b+c$

- This is also valid in algebraic expressions.

We can operate according to the rule: apply the subtraction sign to each of the elements included in the parentheses and always remember that, minus times minus gives plus.

Likewise, we can act according to the order of mathematical operations starting with the parentheses - calculate the difference and only then subtract it.

**For example, in the exercise:**

$33-(9-3)=$

#### Option 1 - according to the rule:

We will separately subtract each element in the parentheses and it will give us:

$33-9+3=$

$24+3=27$

#### Option 2 - according to the order of operations:

$33-6=27$

Click here for a more detailed explanation about subtracting a difference.

Join Over 30,000 Students Excelling in Math!

Endless Practice, Expert Guidance - Elevate Your Math Skills Today

### Division by product

It is also true when we need to divide a certain element by the product of others.

Rule:

**$a:(b\cdot c)=a:b:c$**

- This is also valid in algebraic expressions.

We can operate according to the rule: apply the division to each of the elements included in the parentheses.

Likewise, we can act according to the order of mathematical operations starting with the parentheses - calculate the multiplication and only then divide by the product.

**For example, in the exercise:**

$50:(2\cdot5)$

#### Option 1 - according to the rule:

We will divide separately for each element of the parentheses and it will give us:

$50:2:5=$

First, we will divide $50:2$ and rewrite the exercise:

$25:5=5$

#### Option 2 - according to the order of operations:

$50:10=5$

Click here for a more detailed explanation about division by product.

#### Division by quotient

It is valid when we need to divide a certain element by the quotient of others.

Rule:

$a:(b:c)=a:b\cdot cΒ$

- This is also valid in algebraic expressions.

We can operate according to the rule: apply the division to the first element inside the parentheses and then apply the multiplication to the second element of the parentheses.

Likewise, we can act according to the order of mathematical operations starting with the parentheses - calculate the quotient and only then divide by it.

**For example, in the exercise:**

$48:(6:2)=$

#### Option 1 - according to the rule:

We will apply division to the first element inside the parentheses and then multiply by the second element of the parentheses.

$48:6\cdot2=$

First, we will divide $48:6$ and rewrite the exercise:

$8\cdot 2=16$

#### Option 2 - according to the order of operations:

$48:(6:2)=$

$48:3=16$

Click here for a more detailed explanation about division by quotient.

## Examples and exercises with solutions of arithmetic rules

### Exercise #1

### Video Solution

### Step-by-Step Solution

According to the order of operations, first we solve the exercise within parentheses:

$18+20=38$

Now, the exercise obtained is:

$38-38=0$

### Answer

### Exercise #2

### Video Solution

### Step-by-Step Solution

According to the order of operations, we first solve the exercise within parentheses:

$2+1=3$

Now we solve the rest of the exercise:

$8-3=5$

### Answer

### Exercise #3

### Video Solution

### Step-by-Step Solution

According to the order of operations, we first solve the exercise within parentheses:

$28-3=25$

Now we obtain the exercise:

$22-25=-3$

### Answer

### Exercise #4

### Video Solution

### Step-by-Step Solution

According to the order of operations, we first solve the exercise within parentheses:

$2\times2=4$

Now we divide:

$12:4=3$

### Answer

### Exercise #5

### Video Solution

### Step-by-Step Solution

According to the order of operations, we first solve the exercise within parentheses:

$30-21=9$

Now we obtain:

$100-9=91$

### Answer

Do you know what the answer is?