Direct variation problems use the equation y = kx
Replace y and X with the two known numbers to solve for k:
6=k9
Solve for K by dividing both sides by 9:
k = 6/9, reduces to 2/3
Now replace y and k into the formula to solve for x:
15 = 2/3x
Solve for X by dividing both sides by 2/3:
X = 15 / 2/3
X = 45/2 as an improper fraction, 22 1/2 as a proper fraction or 22.5 as a decimal.
Not sure which format the answer needs to be in, so I gave all three.