finding subscripts in chemistry equations

[Star Struck]

the directions say, "The following equations are balanced, but some of the subscripts have been ommitted. Rewrite the circled compound and supply the missing subscripts."

Here's the problem

P₄O₁₀ + 6H₂O = 4H?PO?

The part after the equal sign is suppose to be circled and the question marks are the omitted subscripts.

Can someone please help me?