they are vertical angles and would be the same so set them to equal each other and solve:
3x-4 = 2x+9
add 4 to both sides:
3x = 2x +13
subtract 2x from each side:
x = 13
now replace x with 13 in the original equations:
3x-4 = 3(13) -4 = 39-4 = 35
2x+9 = 2(13)+9 = 26+9 = 35
the angles = 35 degrees