-7 (3х - 8) + 3 (4х + 5) = 8

-7 (3х - 8) + 3 (4х + 5) = 8
-21х+56+12х+15=8
12х-21х=8-56-15
-9х= - 63
9х=63
х=63/9
х=7
Проверка
-7 (3*7 - 8) + 3 (4*7 + 5) = 8
-7(21-8)+3(28+5)=8
-7*13+3*33=8
-91+99=8
8=8
Ответ: х=7