Question

Subtract 68 from -37.

Answer 1

Hint: First we consider the subtraction of two-digit numbers and then we consider the given numbers. Then we look at the signs of the two numbers. As they are both minus, we can add them and place the minus sign, as minus plus minus is a minus, before the number after adding the two numbers.

Complete step by step answer:
First, let us consider the subtraction between two-digit numbers.
For example, let us take the numbers 73 and 25. While subtracting 25 from 73
$\begin{align}
  & \ \text{ }7\text{ }3 \\
 & \underline{-\ 2\text{ }5} \\
\end{align}$
We need to subtract the units place first and then go to the tens digit next. As we cannot subtract 5 from 3 as 5 is larger than 3, let us borrow 1 from the tens place. Then it converts as
$\begin{align}
  & \ \ \ 6\text{ 13} \\
 & \underline{-\ 2\text{ }5} \\
\end{align}$
Now we subtract 5 from 13 which is equal to 8. Then we subtract 2 from 6 which is equal to 4. Then we get,
$\begin{align}
  & \ \ \ \ 6\text{ 13} \\
 & \underline{\ -2\text{ }5} \\
 & \ \ \ 4\text{ 8} \\
\end{align}$
Hence, we get 73-25=48
The numbers we are given are 68 and -37.
We need to subtract 68 from -37.
$\begin{align}
  & -\text{ }3\text{ }7 \\
 & \underline{-\text{ 6 8}} \\
\end{align}$
Now let us consider a property, when minus is added to minus, we get the symbol minus.
As we can see above that both are minus symbols, we can add them and we get the symbol minus after addition. So, we get
Now let us add the numbers in units placed first, that are 7 and 8.
$\begin{align}
  & -\text{ }3\text{ }7 \\
 & \underline{-\text{ 6 8}} \\
 & \ \ \ \ \ \ \ 15 \\
\end{align}$
Now let us add numbers in the tens place. Then we get,
$\begin{align}
  & -\text{ }3\text{ }7 \\
 & \underline{-\text{ 6 8}} \\
 & -\ 9\ \ \ 15 \\
\end{align}$
As we need only one digit in units place, we need to add 1 to 9.
$\begin{align}
  & -\text{ }3\text{ }7 \\
 & \underline{-\text{ 6 8}} \\
 & -\ 10\ \ 5 \\
\end{align}$
So, we get -105.
Hence the answer is -105.

Note:
The common mistake that happens while solving this type of question is one might understand the question wrongly. We are asked to find the value when 68 is subtracted from -37, one might misunderstand it as $68-\left( -37 \right)$.
Then we apply the property minus minus is plus and we get 68+37 and we get 105 as answer, which is almost near to our answer except the minus sign. So, one needs to understand the questions carefully.