How do i solve this proportion with a variable?

do cross multiplication

y×25=15×20

25y=300

y=12

107

Step-by-step explanation:

Hi, to answer this we have to write an equation for  Colin's score (C) and another equation for Brian's score (B).

Colin scored 36

C =36

Brian scored 35 more than Colin.

B = C +35

Replacing C by 36 in Brian's score equation:

B = (36) +35 = 71

To calculate the combined score we have to add both scores:

C +B = 36 +71 = 107