a) 2^12 :2^22 = 2^(-10) = (1/2)10
b)15^7
c)(2^9)^2= 2^18
d) (2^3)^24 /(2^4)^18= 2^72/2^72=1
e)(5^3)^12/ (5^2)^17= 5^36/5^34=5^2=25
f)81^36/27^48=(3^4)^36/(3^3)^48=3^144/3^144=1
g)(7^13)^2/49^84=7^26/7^168=7^(-142)=(1/7)^142
h)(3^7)^2/81^12=3^14/(3^4)^12=3^14/3^48=3^(-34)=(1/3)^34