a) 2^7 * 5^6 = 2 * 2^6 * 5^6 = 2 * 10^6
b) 0,2^7 * 5^3 = 5^-7 * 5^3 = 5^-4
c) (2/3)^7 : (4/9)^5 = (2/3)^7 : (2/3)^10 = (2/3)^-3 = (3/2)^3
