7. You are given two angles and their sum, all in terms of x. Set the sum equal to the sum:
... (4x -1) +(2x +15) = (8x +8)
... 6 = 2x . . . . collect terms, subtract 6x+8
... 3 = x . . . . . divide by 2
To find the angles, fill in this value for x
∠AOB = 4·3 -1 = 11
∠BOC = 2·3 +15 = 21
∠AOC = 8·3 +8 = 32
8. Same deal.
... ∠BOC + ∠COD = ∠BOD
... (3x -10) +(8x +13) = (12x -6)
... 9 = x . . . . . . . . subtract 11x-6
And the angle values are ...
∠BOC = 3·9 -10 = 17
∠COD = 8·9 +13 = 85
∠BOD = 12·9 -6 = 102