they add to 180
x+y+z=180
smallest (lets say that's x) is 36
36+y+z=180
minus 36 both sides
y+z=144
each term is the common difference away from the next term
z=y+d
y+y+d=144
and also
36+d=y so
36+d+36+d+d=144
3d+72=144
minus 72 both sides
3d=72
divide both sides by 3
d=24
common difference is 24
36+24=60
60+24=84
36+60+84=180
correct
largest angle is 84 degrees
