#### Answer

150 dollars

#### Work Step by Step

I=PRT
Let P=1000dollars , R=10% ,T = 18 months
18 months =$\frac{18}{12}$year=$\frac{3}{2}$
I=1000 $\times$10% $\times$ $\frac{3}{2}$
Write 10% as a decimal
I = 1000$\times$0.10$\times$ $\frac{3}{2}$
Multiply
I= 100$\times$$\frac{3}{2}$ = $\frac{300}{2}$ =150
The simple interest is 150 dollars.