In isosceles △RST, the ratio of the measures of vertex angle, T and the exterior angle at R is 1:5. Find the measure of each interior angle of the triangle.

Question

Please help. Don’t understand 

Answer 1

R=S

R+S+T = 180

2R + T = 180

T:R = 1:5

T/R = 1/5

R=5T

T=R/5

2R + R/5 = 180

11R/5 = 180

R = (5/11)180 = 900/11 = 81 9/11

S = R = 81 9/11 degrees

T = 180 - 2(81 9/11) = 180 - 163 7/11 = 16 4/11 degrees