altitude
 

Can someone answer these, and tell me how to come up with the answer for questions like these?

1) Given an indicated altitude of 10,000, and an actual OAT -20, you set your altimeter to a local station setting of 29.62". If the station elavation is 2,500 ft what is your actual altitude?

2) At a temperture of ISA -25C how much is added to MEA?

Thanks for your help.