12/3 = x/8
Cross multiply
3x = 96
Eliminate
3x/3 = 96/3
x = 32
You must know that the sum of interior angles is 180°. We also know that AC and BA are congruent which means angles B and C are also congruent. To find x we can assume 25=5x. Which makes x=5, and angle C=25°.
Then we can add all the angles to find y and A. 25+25+(3y+70)=180. Then solve for y and then solve for angle A.
The numerator and denominator can be divided by 4 to get 12/25.
48 / 4 = 12
100 / 4 = 25
