We are given with:
x = L + 9
L proportional to y
x = 24, y = 5
y = ?, L = 12
Since we know L is proportional to y, we have the equation:
L = ky
Substituting this to the first equation
x = ky + 9
Using the given conditions
24 = k(5) + 9
k = 3
So,
L = 3y
When L = 12
12 = 3y
y = 4
