The angles are set to equal to eachother since alternate interior angles are congruent
so 6x+5=4x+45
Solve for X
-5 from both sides
6x=4x+40
-4x both sides
2x=40
÷2 both sides
X=20
Now plug in the answer for X in angle A to figure out what degree angle A is 6x+5
6 (20)+5
120+5
