In a game A can give B 25 points in 75 and C 18 points in 90. How many points can C give B in a game of 120?

When A scores 75 points, B scores 50 points.
When A scores 90 points, C scores (90 - 18) = 72 points.
∴ When A scores 75 points, C scores = 72 × 75 / 90 = 60 points.
A : B : C = 75 : 50 : 60
C : B = 60 / 50 = 120 / 100
So, in a game of 120, C can give B
(120 - 100) = 20 points.