What don't you understand about my previous answer?
http://www.jiskha.com/display.cgi?id=1335465650
How do you use prime factorization to reduce a fraction?
2 answers
factor the numerator and the denominator, then cancel values which appear in both places.
for example,
810/36 = 2*3^4*5/2^2*3^2 = 3^2*5/2 = 45/2
for example,
810/36 = 2*3^4*5/2^2*3^2 = 3^2*5/2 = 45/2