130 srv is a straight line so angleSRV=180 TRV and SRT make up SRV so TRV + SRT = SRV. (x-10) + (2x+10) = 180. the 10s cancel each other out so 3x = 180 so x=60 bc 180/3=60. sub 60 for x in TRV and u get 130. sub 60 for x in SRT and you get 50, which, with 130 makes 180, so the answer is correct!