Question 1944
{{{((6a^5)(b^7)(c^6))/((-3a^3)(b^9)(c^6))}}}

this becomes...

{{{((-2a^2))/(b^2)}}}

since you just subtract the powers...so 

for a: 5-3=2
for b: 7-9=-2...therefore 2 on the bottom
for c: 6-6=0...they cancel each other

jon.