a: 3*5^2+15*2^2=3*25+15*4=135
17*2^2-2*5^2=18
=> >
b: 30-2^25:2^23=30-4=26
3^5:(1^10+2^3)=3^5:3^2=3^3=27
=> <
c: 2^2*3-(1^10+8):3^2=12-1=11
5^2*3^2-25*2^2=225-100=115
=> <
d: 4^20:(4^15*7+4^15*9)
=4^20:4^17=4^3=64
3*5^2-6^2+5^2=5^2*4-6^2=100-36=64
=> =