A = 157, B = 23 The definition of supplementary angles is that they add up to 180 degrees. So A+B = 180. And A = 7B - 4. So write down the formula A + B = 180 Substitute the formula for A in terms of B 7B - 4 + B = 180 Combine terms 8B - 4 = 180 Add 4 to both sides 8B = 184 Divide both sides by 8 B = 23 Now calculate A in terms of B A = 7B - 4 A = 7 * 23 - 4 = 161 - 4 = 157 Verify that A and B add up to 180 157 + 23 = 180