The angles A and B are alternate interior angles, and as such their measure is the same.
This leads to the equation
[tex]8x+6=4x+38 [/tex]
Subtract 4x and 6 from both sides to get
[tex] 8x-4x = 38-6 [/tex]
which simplifies to
[tex] 4x = 32 [/tex]
Plug this value for [tex] 4x [/tex] in the expression for [tex] B [/tex] to get
[tex] B = 4x+38 = 32+38 = 70 [/tex]
