Solve Vertical Subtraction: 91 minus 7 Step-by-Step

To solve the subtraction problem $91 - 7$, we'll align the numbers vertically and perform the operation step by step.

Step 1: Align the numbers vertically:

$\begin{aligned} &91 \\ -& \\ &~~7 \\ \end{aligned}$

Step 2: Subtract the units:

The units digits are $1$ from $91$ and $7$. Notice that $1$ is less than $7$, so we need to borrow from the tens digit of $91$.

- Regroup the tens and units: Borrow $1$ ten from the tens place $9$:
$91$ becomes $8$ in the tens place and $11$ in the units place, represented as:

$\begin{aligned} 8~11& \\ -~~~~ 7~& \end{aligned}$

Step 3: Perform the final subtraction:

- Subtract the units: $11 - 7 = 4$.

- The tens remain $8$, so the resulting number is $84$.

Therefore, the solution to the problem is $84$.