Question

Name or state the postulate, property, definition, or theorem that justifies the statement.

If $a+7=4$, then $a=-3$.

Short answer

The property that justifies the statement is Property of algebra.

Step-by-step solution

Step 1. State the concept to be used.

To justify the statement “If $a+7=4$, then $a=-3$”, the properties of algebra will be used.

Step 2. Show the calculation.

Consider, $a+7=4$.

Subtract by 7 on both sides,

$\begin{array}{c}a+7-7=4-7\\ a=-3\end{array}$

Hence, the statement is justified.

Step 3. State the conclusion.

Therefore, the statement is justified by the property of algebra.