7. 15 - 5(4c - 7) = 50

Explanation:

Step1: Expand the expression

$15-5\times4c + 5\times7=50$, which simplifies to $15-20c + 35 = 50$.

Step2: Combine like - terms

$(15 + 35)-20c=50$, so $50-20c = 50$.

Step3: Isolate the variable term

Subtract 50 from both sides: $50-50-20c=50 - 50$, resulting in $-20c=0$.

Step4: Solve for c

Divide both sides by - 20: $c=\frac{0}{-20}$.

Answer:

$c = 0$