1.064x10 to the power of -19 - 8.074x10 to the power of -20

$${\mathtt{1.064}}{\mathtt{\,\times\,}}{{\mathtt{10}}}^{-{\mathtt{19}}}{\mathtt{\,-\,}}{\mathtt{8.074}}{\mathtt{\,\times\,}}{{\mathtt{10}}}^{-{\mathtt{20}}}$$

 

$$\\10^{-20}(1.064*10-8.074)\\
=10^{-20}(10.64-8.074)\\
=2.566\times 10^{-20}$$

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