#### Answer

$$5.6 \times 10^{13} + 3.1 \times 10^{13} = 8.7 \times 10^{13}$$

#### Work Step by Step

$$5.6 \times 10^{13} + 3.1 \times 10^{13}$$
Since both expressions have the same value of exponents in 10, we can just proceed by adding the numerical values.
Thus,
$$5.6 \times 10^{13} + 3.1 \times 10^{13}$$ $$(5.6+3.1) \times 10^{13}$$ $$= 8.7 \times 10^{13}$$