First you need to solve for "x": 6x+3=8x-21, 3=2x-21, 24=2x, x=12. Then plug in number 12 to your equation: 6(12)+3=75; Just to make sure that I solved correctly for x, plug in 12 into the second equation: 8(12)-21=75. Yahoo, the x is 12 and angle measure is 75°.
You subtract 3 from both sides to make it 6x=8x-18. Then you subtract 8x from both to make it -2x=-18. Then divide by -2 on both sides and it comes out to x= 9.
