Pls halp on formulas involving polygons

The sum of all five angles is 540 degrees.
A) 4*congruent angles + 5th angle = 540
B) (5th angle) -30 = 2*cong angle

A) 5th angle = 540 -4*cong angle
B) 5th angle  = 2*(cong angle)   -30
Multiplying B) by -1
B) -5th angle  = -2*(cong angle)   +30  then adding to A)
A) 5th angle = 540 -4*cong angle

-2*(cong angle)   +30  = 540 -4*cong angle
2*(cong angle) = 510

By trial and error I determined
each congruent angle = 95
5th angle = 160