Respuesta :

Answer:

x is 10.

Step-by-step explanation:

3x + 12 = 42

Subtract 12 from both sides

3x = 42 - 12

Subtract 12 from 42 to get 30

3x = 30

Divide both sides by 3

x = 30/3

Divide 30 by 3 to get 10

x = 10