## Question

`If a : b = 20:5 then find out the value of (13a-9b): (11a-7b)?`

A. 43/42

B. 40/33

C. 43/37

D. 44/37

**Answer: C – 43/37**

**Solution:**

**a : b = 20 : 5**

a/b = 20/5 = 4

=> **a = 4b**

**=> (13a – 9b) : (11a – 7b)**

=> (13 (4b) – 9 (b)) **/** (11 (4b) – 7 (b))

=> 52b – 9b **/** 44b – 7b

=> 43b **/** 37b

`=> 43/37`

**(13a – 9b) : (11a – 7b)** Answer is **43/37**.