When you add the degrees of all the angles in a triangle you should get 180
A= 5x+5
B= 90
C= 3x+5
5x + 3x = 8x
5 + 90 + 5 = 100
8x + 100 = 180 this is the equation
-100 -100
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8x = 80 ➡️ divide BOTH sides by 8
x = 10
Now plug 10 into angles A and C
5(10)+5= 55
3(10)+5= 35
A= 55 , B= 90 , C=35