Since angles A and C are equivalent, then angles B and D must also be equivalent. So if
angle B = angle D then...
7x + 15 = 8x
Now we just solve for x
7x + 15 = 8x
15 = 8x - 7x
15 = x
We Can check to see if it is correct by substituting 15 in for x in the equation..
7x + 15 = 8x
7 (15)+15 = 8 (15)
105 +15 = 120
120 = 120
It checks! angles B and D = 120 degrees
