Question

if a:b =5:4 then find 3a+4b/ 2a+5b =?

Answer 1

I think its 31/30 because 
let a=5
and b=4
then
3(5)+4(4)/2(5)+5(4)
15+16/10+20
=31/30

Answer 2

Hi ,

a : b = 5 : 4

Let a = 5x ,

b = 4x

( 3a + 4b )/( 2a + 5b )

= [ 3 × 5x + 4 × 4x ] / [ 2× 5x + 5 × 4x ]

= ( 15x + 16x ) / ( 10x + 20x )

= 31x / 30x

= 31/30

= 31 : 30

I hope this helps you.

:)