Step-by-step explanation:
(4y-y)(9+4x+3y)
36y+16xy+12y^2-9y-4xy-3y^2
collect like terms
36y-9y+16xy-4xy+12y^2-3y^2
=27y +12xy+9y^2
Given that,
y varies directly with x and y = 10 when x = 20.
To find,
The value of y when x = 15.
Solution,

Put x = 20 and y = 10

Put k = 1/2 and x = 15 to find the value of y.

So, the value of y is 7.5
So listen to your teacher next time
Answer:
12
Step-by-step explanation:
hope it helps