Answer: Step 4
Step-by-step explanation:
Rena made the first mistake in step 4 because she left the terms [tex]2^{3} and (-1)^{21}[/tex] in the denominator, when in the previous step they were also in the denominator but raised to -1, which means that they should be in the numerator.
The right step 4 would be:
[tex]\frac{2^{3} (-1)^{21} }{2^{6} } =\frac{-1}{2^{3} } =\frac{-1}{8}[/tex]
