71) The triangle is isos. so the base angles are congruent
2a+b=5b-3a
5a=4b
The angles of a triangle all add up to 180
180=5a -2b + 2a +b + 5b -3a
180=4a+4b
Substitute 4b with 5a
180=4a+5a
180=9a
a=20
And substitute a into the equation: 5a=4b to solve for b and solve for the measurements of the angles
72) Angles that are supplementary add up to 180
8(y-x)+124=180
9x-2y+124=180
8x-8y=56
(9x-2y=56)4
Use elimination to solve for the variables
8x-8y=56
-(36x-8y=224)
-28x=-168
x=48
Substitute x into the other equation to solve for y and find the measurements of the angles