Solve Addition Equation: Find Missing Number in 33 + □ = 42

To solve the problem $33 + \Box = 42$ using the number line, we will make strategic jumps:

First, jump from 33 to the nearest higher round number, which is 40:

• This first jump is $40 - 33 = 7$.

Next, jump from 40 to 42:

• This second jump is $42 - 40 = 2$.

Add the two jumps to find $\Box$:

• $\Box = 7 + 2 = 9$

Therefore, the solution to the problem is $9$.