Paul and Donna invest $12,000, part at 5% simple interest and the rest at 7% simple interest for a period of 1 year. How much money did they invest at each rate it their total annual interest from both investments was $800? (I=prt)

Let x , y be the amount of investemnts made by Paul and Donna.

x+y=12000.

0.05x+0.07y=800.

0.05x+0.07(12000-x)=800.

0.05x+840-0.07x=800.

0.02x=40.

x=40/0.02

=2000.

y=12000*2000

=10000.