Jika a:b=3:4,maka(6a+6b):(4a+5b) adalah..

a : b = 3 : 4
a = 3/4 b

(6a + 6b) : (4a + 5b)
= 6(a + b) : (4a + 5b)
= 6( 3/4 b + b) : (4 . 3/4 b + 5b)
= (6 . 7/4 b) : ( 3b + 5b)
= 21/2 b : 8b
= 21 / (2 × 8)
= 21/16