directly varies for that mean if y increases x will increase too and the other way around if y decreases x will decrease too.
an easy way to solve this is to make all values into fraction ik it sounds confusing lemme explain it. so if we say [tex]\frac{x}{y}[/tex] and add the values of the known [tex]\frac{3}{9}[/tex] we can say that if [tex]\frac{x}{15}[/tex] is equal to [tex]\frac{3}{9}[/tex]
now we just solve it for x
[tex]\frac{x}{15} = \frac{3}{9} \\9x = 45\\x= 5[/tex]
hence when y is 15 x will be 5
