In order to solve this equation, we can isolate the variable, x. This will allow for us to be able to solve for the value of x more clearly. We can take the positive 8 that is to the left of the equal and bring it to the other side, where the 21 is. But this will require us to change the sign of the 8. When we move the 8 to the right of the equal side, the 8 will turn negative. This will isolate the x and give us a more clear answer: x=21-8. 21-8 is equal to 13, hence x is equal to 13.
ANSWER: 13