So a line is 180° Since it gave you options, the easiest way would be to plug it in (plug and chug) the answer is 11 first what I did was plug 12 into 5x+10 and then found the answer and then added 58° the answer of that subtracted from 180 with that I then plugged in 11 for x for 11x+2 = 123 180 - 123 = 57 which is the same answer for the missing angle within the triangle
