Correct Answer - Option 3 : - 16/143
Given
c : d = 9 : 10
Calculation
(6c - 7d)/(7c + 8d)
⇒ [6(c/d) - 7(d/d)]/[7(c/d) + 8(d/d)]
⇒ [6(9/10) - 7]/[7(9/10) + 8]
⇒ [(54/10) - 7]/[(63/10) + 8]
⇒ [(54 - 70)]/[(63 + 80)/10]
⇒ - 16/143
∴ Value of (6c - 7d)/(7c + 8d) is - 16/143