The base of a rectangluar prism is 5 meters by 3 meters. the height of the prism is 7 meters. the total surface area, except for one face, is 121 square meters. What are the dimesions of the missing face?

Total SA = top + bottom + 2 (short side) + 2 (long side)

top = bottom = 5*3 = 15

short side = 7*3 = 21

long side = 7*5 = 35

SA = 2 (15) + 2 (21) + 2 (35) = 30+42+70 = 142

So 142 - 121 = 21, so the missing face is a short side of 7*3