It's important to understand that vertical angles are always ≅.
So we can say that the m<A = m<B.
So we can setup the equation 7x - 20 = 6x - 1.
Start by subtracting 6x from both sides and we have x - 20 = -1.
Now add 20 to both sides to get x = 19.
If x = 19, then the m<A is 7(19) - 20 or 133 - 20 which is 113.
