Method 1: By writing the exponents as repeated multiplications,
breaking 4 into prime factors and cancelling:













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Method 2: By adding exponents to multiply and then subtracting
exponents to divide:





Divide the -12 on the top by the 2 on the bottom, getting -6 on the
top.

Subtract the exponents of "a", 7-4 getting exponent 3 and putting 
a3 on the bottom because the larger exponent of "a" was 
on the bottom.

Subtract the exponents of "b", 3-1 (understood) getting exponent 2 
and putting b2 on the top because the larger exponent of 
"b" was on the top. 



Edwin