Question

The variables y and x have a proportional relationship, and y = 5 when x = 4.

Answer 1

If the variables y and x have a proportional relationship, we have

$xy=k$

Since (x,y)=(4,5) is a valid pair, we know that

$xy=20$

So, if y = 8, we have

$8x=20 \iff x=\dfrac{20}{8}=\dfrac{5}{2}$