angle C and D are supplementary angles and measure of angle C is twice angle D. find measure of angle C and D

Question

 it is very hard can someone please help

Answer 1

m<C+m<D=180º

m<C=2*m<D

substitute

2*m<D+m<D=180º

3D=180

D=180/3

D=60

m<D=60º

m<C=2*60=120º