If (a + b) : c = 7 : 9 , (b + c) : a = 13 : 3 , then (a + c) : b = ?

3 : 1

In these type of questions always note that the total amount/ratio must be same in all conditions.

⇒ (a + b) : c = 7 : 9  = 16 (total)

⇒ (b + c) : a = 13 : 3 = 16 (total)

total equal is already equal,

Therefore,

a = 3 , c = 9 & b = 16 -(3 + 9) = 4

Here,

⇒ (a + c) : b = 12 : 4  = 3 : 1