To figure out figure 18 you would first figure out x and a triangle equals 180 so 180- (36+46) which is 180-82= 98 and then there are vertical angles between the right and left side so x is equal to one of the angles on the right so 98+44= 142 and 180-142= 38
Then to figure out figure 19 you would first find y by adding 39 and 91 to get 130 and 180-130=50 and then 180-91 (for the angle in the bottom right for the left triangle) is 89 so 89+71=160 and 180-160 is 20.