Question

When you solve the equation x plus nine equals fifteen, how do you know what number to subtract from both sides? Why is it important to subtract the same number from both sides of the equation?

Answer 1

x + 9 = 15

You know that you should subtract 9 from both sides because when solving equations, the variables should be on one side and the the constants should be on the other. It is important to subtract the same number from both sides because this keeps the equation balanced, and will change as the inverse operations are performed.