To find out how much Grace saved last December, you can calculate three-tenths of her paycheck.
Grace's paycheck = $2,500
She saved three-tenths of it, which can be calculated as follows:
\[ \text{Savings} = \frac{3}{10} \times 2500 \]
Calculating that:
\[ \text{Savings} = 0.3 \times 2500 = 750 \]
So, Grace saved $750 last December.
The correct response is $750.