Question

quantônio e 9+2(5X-4)=21

Answer 1

9 + 2 ( 5x - 4 ) = 21

9 + 10x - 8 = 21

10x = 21 - 9 + 8

10x = 20

x = 20/10

x = 2

Answer 2

9 + 2 (5x - 4) = 21
9 + 10x - 8 - 21 = 0
10x + 9 - 8 - 21 = 0
10x + 1 - 21 = 0
10x - 20 = 0
10x = 20
x = 20 / 10
x = 2

Espero ter ajudado. Valeu!