Question

МАТЕМАТИКА!!!! (5+7а)15 = -30

Answer 1

5*15+7a*15+30=0
105a+105=0
105a=-105 - делим на 105
a=-1

Answer 2

(5+7а)15 = -30
75+105a= -30
105a= -30-75
105a= -150
a= $\frac{-150}{150}$ = -1
Ответ: a= -1