Question

How do you write a direct variation equation that relates x to y and y = 4 when x = 2, then how do you find y when x = 16?

Answer 1

I would write it as:
`y=k*x` where `k` is a proportionality constant to be found using:
`x=2 -> y=4`
Giving:
`4=k*2` and `k=4/2=2`
So your equation is:
`y=2x`

When `x=16`, `y=2*16=32`