the simlified product of this is?

10a power of 8.9r power of 4
_______ _____________
3r power of 2 100a

i dunno what to do?

Start by writing the problem using symbols most people can understand (NOT words),with parentheses where needed for clarification. I assume your expression is:

10a^8*9r^4/[3r^2*100a]
Next, note that
10/100 is 0.1
9/3 is 3
a^8/a = a^7
r^4/r^2 = r^2
Make the appropriate cancellations and you get
0.3 a^7*r^2

(* denotes multiplication)