#### Explanation:

The formula for simple interest is $S I = \frac{P R T}{100}$
We know all the values except the amount to be invested, $P$

Re-arrange the formula and substitute the known values:

$P = \frac{100 \times S I}{R T} = \frac{100 \times 500}{8 \times 2}$

P = $3125 Check: $S I = \frac{3125 \times 8 \times 2}{100}$=$500