Stephanie,
First, as you would when both are positive, factor the numerator, factor the denominator and then look for any cancellation.
32 = 1 2 2 2 2 2
40 = 2 2 2 5
Thus ^{32}/_{40} = ^{(1 2 2 2 2 2)} /_{(2 2 2 5)} = ^{(1 2 2)} /_{5} = ^{4}/_{5}
Penny
