I got 9 because you have to plug in answer (7, 9, 11, 8) in each equation than add them both together. I first plugged in 7 for x in the equation 9x-5. I got 58. I plugged in 7 for x in the equation 5x+12 and got 47. When I added both the answers together I got 105. The answer was to low because SU has to be 133. I plugged in 9 for x in both equations then added them both and got 133 for SU. I hope this helps.
