15= а+80-89/2

To solve the equation \( 15 = a + \frac{80 - 89}{2} \), we can first simplify the right side.

1. Calculate \( 80 - 89 \): \[ 80 - 89 = -9 \]

2. Now, divide by 2: \[ \frac{-9}{2} = -4.5 \]

3. Substitute back into the equation: \[ 15 = a - 4.5 \]

4. To isolate \( a \), add \( 4.5 \) to both sides: \[ a = 15 + 4.5 \] \[ a = 19.5 \]

Thus, the solution is \( a = 19.5 \).