Question

If `y` varies directly with `x` and `y=20` when `k=4`, what is the value of `x`?

Answer 1

`5`

Explanation:

If `y` is directly proportional to `x` then there exists `k in RR` such that `y=kx`.
In this case, `y=4x`.

Hence `x=y/k=20/4=5`

Graphically :

graph{4x [-46.22, 46.25, -23.1, 23.16]}