How do you answer fifo lifo weighted average? Is their a specific formula I can use?

It depends on whether it's periodic or perpetual. And it's more of a method than a formula.

Since you can apply all three of those methods to both periodic and perpetual (i.e. six total ways to do it), that would get kind of long to demonstate all of them. So here's a link that shows examples in Parts 2, 3 & 4.

Inventory and Cost of Goods Sold | AccountingCoach.com