7. \frac{-5}{a+5}- \frac{10}{2(a+5)}- \frac{8a}{4(a+5)} = -\frac{2a}{a+5} = \frac{2*5}{19(- \frac{5}{19} +5)}= \frac{10}{-5+95}= \frac{1}{9}
8. ∠ACB = ∠ACD-∠BCD = 180-92 = 88
∠BAC = ∠ACB = 88
∠ABC = 180 - ∠BAC - ∠ACB = 180-88-88 = 4
∠FBC = ∠ABF - ∠ABC = 180 - 4 = 176
9. ∠AOL + ∠BOK = 252
∠AOL = ∠BOK
252/2 = 126
∠AOK = ∠KOL - ∠AOL = 180-126 = 54