Question

Variable y varies directly with variable x, and y = 5 when x = 8.

What is the value of x when y = 15?

Answer 1

do you know the equation for direct variation ??

Answer 2

no

Answer 3

hmm equation for direct variation is \[\huge\rm y = kx \]
where k is constant of variation
so first replace x and y by their values and then solve for k