1) Since it is an isosceles triangle, the angle at T should be the same as that at R
2)A straight line adds up to 180 degrees, hence:
(3x-50)+7x should equal 180
proceed to solve the equation like so...
10x - 50 = 180
10x = 180 + 50
10x = 230
x = 230/ 10
x= 23
so the answer is A) x = 23