Question

Find each sum or difference.

$31-42.9$

Short answer

The value of the expression is –11.9.

Step-by-step solution

Step 1. Concept of addition and subtraction.

Two numbers with similar signs get added and the resulting number carries the similar sign.

Two numbers with opposite signs get subtracted and the resulting number carries the sign of the larger number.

Step 2. Apply the concept of like and unlike signs.

If there is a sign like $+\left(+\right)$or $-\left(-\right)$then the resulting sign will be positive and if there is an unlike sign $+\left(-\right)$or $-\left(+\right)$then the resulting will be negative.

$=-71+10$

Step 3. Evaluate the difference.

$\begin{array}{l}=-42.9+31\\ =-11.9\end{array}$

Therefore, the sum is –11.9.