Let s and c be the rate of the boat in still water and the rate of the current, respectively. Then: 108/s-c=3 108/s+c=2 3s-3c=108 2s+2c=108 Solve for s and c ☺☺☺☺
Since angles 3 and 7 are corresponding angles, they are also congruent. This means that angle 3 is equal to angle 7. Therefore, the correct answer is C, 120 degrees.