The total sum of angles in a triangle is 180, thus the value of ∠ACB will be obtained as follows: Given that the triangle is a right triangle, the sum of angles will be: (4x)°+(7x-20)°+90=180 simplifying and solving for x we get: 4x+7x-20+90=180 11x=180+20-90 11x=110 dividing both sides by 11 we get: (11x)/11=110/11 this gives us x=10° Thus substituting the value of x in: ∠ACB=(7x-20)° =(7*10-20) =70-20 =50°
