a x=12
the sum of angles in a triangle is 180
53+39+4+7x=180
96+7x=180
7x=86
x=84/7
x=12
b. sum of angles in a triangle is 180
5x+(6x-5)+75=180
5x+6x-5+75=180
11x+70=180
11x=180-70
11x=110
x=110/11
x=10
that's how to solve it
