#### Answer

700 dollars

#### Work Step by Step

I=PRT
Let P=2500dollars , R=16% ,T = 21 months
21 months =$\frac{21}{12}$ year = $\frac{7}{4}$
I = 2500 $\times$16% $\times$ $\frac{7}{4}$
Write 16% as a decimal
I = 2500$\times$0.16$\times$ $\frac{7}{4}$
Multiply
I = 400$\times$$\frac{7}{4}$ =$\frac{2800}{4}$=700
The simple interest is 700 dollars.