Remember, these are quadrilaterals, so they must add up to 360°. Just add up the angles and then do 360 minus that number to solve for x. Therefore: 1. 118 + 90 + 99 = 307 360 - 307 = 53 2. 110 + 96 + 78 = 284 360 - 284 = 76 3. 48 + 118 + 97 = 263 360 - 263 = 97 4. 105 + 99 + 64 = 268 360 - 268 = 92 5. 103 + 63 + 113 = 279 360 - 279 = 81 6. 95 + 80 + 88 = 263 360 - 263 = 97