Objectives Solve equations using addition and subtraction
Addition Property of Equality If a, b, and c are any real numbers, and a = b, then: a + c = b + c and c + a = c + b
Subtraction Property of Equality If a, b, and c are any real numbers, and a = b, then: a - c = b - c
Solving Addition and Subtraction Equations When solving equations, remember that addition and subtraction are inverse operations - they undo each other (i.e., 10 + 9 - 9 = 10). To solve equations using addition and subtraction, first decide which operation has been applied, then use the inverse operation to undo this (remember to add or subtract from both sides of the equation). 1. Solve: x + 79 = 194 Solution: x + 79 = 194 x + 79 - 79 = 194 - 79 x = 115 You need to get the variable by itself (isolate the variable). To undo adding 79, subtract 79 from both sides. 2. Solve: x - 56 = 604 Solution: x - 56 = 604 x - 56 + 56 = 604 + 56 x = 660 You need to isolate the variable. To undo subtracting 56, add 56 to both sides.