An unknown compound has a molecular formula?

An unknown compound has the following chemical formula:
PxCl5 (Small x and 5)
Where x stands for a whole number.
Measurements also show that a certain sample of the unknown compound contains 9.70mol of phosphorus and
48.31mol of chlorine.
Write the complete chemical formula for the unknown compound.

I'm confused I know how to write the formula when given the percentages but not given the moles. So am I meant to convert those into percentages? Thanks for helping :)