Respuesta :
Answer:
multiple 6 with numbers inside paranthesis:
12x - 66 + 15 = 21
add 66 fhen substrack 15 from both sides :
12x = 72 divide both sides with 12:
x = 6
Step-by-step explanation:
In his answer above he didn’t add 81 to both sides. (Somebody correct me if I’m wrong)