Respuesta :
-3(b - 7)...distribute thru the parenthesis...that means multiply 3 by everything in the parenthesis to get rid of the parenthesis
(-3 * b) - (-3 * 7) = -3b - (-21) = -3b + 21 <==
(-3 * b) - (-3 * 7) = -3b - (-21) = -3b + 21 <==