The explanation is that the the supplementary angle to 80 is 100 since a straight line has an angle of 180, now the 100 degree angle is congruent to the angle x + 25 which means that x + 25 is equal to 100 so x is 75
Because we know that the top angle is 80, we now know that the top angle below is also 80. A line is 180 degrees. So when you 180 - 80, you get 100. Because it says x + 25, you know the total is 100. so its X + 25 = 100 X = 100 - 25 X = 75 sorry if this was confusing i tried my best, hope this helps!!
