Respuesta :

Since angle A = Angle B, I believe you would write it out like this:
6x+12=3x+63
subtract 3x from both sides, then subtract 12 from both sides.
3x=51
divide 51 by 3 to find x.
x=17
Now to find the measure of angle A.
A = 6(17)+12
A = 102+12
A = 114, angle A is 114 degrees.

From the fact that the two horizontal lines are parallel, you can deduce <A=<B

so you can equate the two right-hand sides of the equations:

6x+12=3x+63 and solve for x

3x = 51

x= 17 degrees is the measure <A (and <B as well)