Question

como resolvo 4(x+5)+3(x+5)=21

Answer 1

$4(x+5)+3(x+5)=21\to \\\\ 4x+20+3x+15=21\to \\\\ 4x+3x=21-20-15\to \\\\ 7x=-14\to \\\\ x=- \frac{14}{7} \to \\\\ \boxed{x=-2}$