The exponent Marina should use for b is: D. 7.
When dividing, you subtract the exponents. I.e. [tex]a^m \div a^n = a^{m - n}[/tex].
Using the rule, we would also subtract the exponents of b in the simplified expression. Thus:
[tex]b^4 \div b^{-3}[/tex]
Subtract the exponents
4 -(-3) = 4 + 3 = 7.
Therefore, the Maria should use the exponent b = 7.
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