3 GMAT Problems Please Help

Problem 1: (.8)^-5 / (.4)^-4 = Problem 2: Account X interest rate = 6% Account Y interest rate = 8% The total invested in these accounts was $50,000 and it increased 7.2% How much was invested in Account X? Problem 3: There are 4 integers. There sum and product is even. What is the max odd numbers y...