LBO Technicals from EB (Please help)

I can't figure these out, would appreciate help from someone with more experience on how to think through them.

given a 12x entry, 10% margin, 0% cash conversion, 5 years time, 10x ebitda, 14% cagr, 100% equity: what is the IRR?

A and B own 50% each of a company. Ebitda 50mm, 10x multiple, A wants to buy B's 50% stake for 25mm. Leverage ratio is 3x. rest is funded by PE Firm P. What is P's share of company?
5 years later, PE Firm X wants to buyout company. ebitda is 150mm, 20x multiple. what is P's IRR?