Question

What is the solution to the equation?  5(8 + 7) = 5 • x + 5 • 7   A. x = 1   B. x = 5   C. x = 7   D. x = 8

Answer 1

$5(8+7)=5\cdot x+5\cdot7\\\\x=8\\\\Answer:D\\\\5\cdot x+5\cdot7=\underline{5}\cdot x+\underline{5}\cdot7=\underline{5}\cdot(x+7)=5\cdot(8+7)\iff x=8$