Respuesta :

Answer: + or - in between the 3x and 6? Can be either 7 or 3

Step-by-step explanation:

3x+6=15.

Subtract '6' on both sides.

3x=9.

Divide by '3'.

x=3

3x-6=15.

Add '-6' on both sides.

3x=21

Divide by '3'.

x=7

Again, it solely depends on your sign in between the first two numbers.