Question

y varies directly with x, and y = 12 when x = 5. What is the value of y when x = 8?

Answer 1

y varies directly as x means y=kx or k=y/x where k is the constant of variation
find k

y=12 and x=5
k=12/5
y=kx
when x=8
y=(12/5)(8)
y=96/5

Answer 2

y=x/k
12=5/k
k=5/12

k= x/y
5/12=8/y
y = 12×8/5
y = 96/5
y= 19.05