3x = 15 can be solved with the Multiplication Property of Equality. In order to solve this equation, x must be isolated. So, if we multiply both sides by 1/3, then x's coefficient will become 1. 15 times 1/3 (15 * 1/3 = 15/3) equals 5. Thus x = 5. You can double check my work by substituting x with 5.
