#### Answer

$$7.1 \times 10^{-3}$$

#### Work Step by Step

To write a decimal in scientific notation, we move the decimal to the left or right until we are left with one number only to the left of the decimal.
For $0.0071$, we need to move the decimal point three places to the right to get $7.1$. When we move the decimal point to the right, we get a negative exponent; conversely, if we move the decimal point to the left, we get a positive exponent. Therefore, we have to multiply $7.1$ by a multiple of $10$ raised to a negative power. The value of the exponent depends on how many places we moved the decimal. In this case, we moved the decimal three places to the right, so the exponent will be $-3$:
$$7.1 \times 10^{-3}$$