When we talk about direct variation we mean the following relationship between variables:
[tex]y=kx[/tex]where "k" is a constant. We must determine the value of this constant. To do that, we use the fact that when y = 18, x = 13, we replace that in the relationship:
[tex]18=k(13)[/tex]Now we solve for "k", dividing both sides by 13, like this:
[tex]\frac{18}{13}=k[/tex]solving we get;
[tex]k=1.38[/tex]We replace this value in the relationship:
[tex]y=1.38x[/tex]Now we are asked the value of "y", when "x = 63", we replace x = 63 in the relationship, we get:
[tex]\begin{gathered} y=1.38x \\ y=1.38(63) \end{gathered}[/tex]solving we get;
[tex]y=87.23[/tex]Therefore, y = 87.23 when x = 63
