Answer
$$8.82\times 10^{-18}.$$
Work Step by Step
By subtracting the exponents and dividing the like terms, we have
$$\frac{ 450\times 10^{-12} }{51\times 10^{6}}=\frac{ 450}{51} \times 10^{-12-6} \\
=8.82\times 10^{-18}.$$
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