To solve the equation \( 15 - a = 43 \), follow these steps: 1. Subtract 15 from both sides to isolate the term with \( a \): \[ -a = 43 - 15 \] 2. Simplify the right side: \[ -a = 28 \] 3. Multiply both sides by -1 to solve for \( a \): \[ a = -28 \] Thus, the solution is: \[ a = -28 \]