algebra
posted by matt on .
two investments were made totaling $15,000. for a certain year these investments yielded $1432 in simple interest. part of the $15,000 was invested at 9% and part at 10%. find the amount invested at each rate.
a total of $1150 was invested, part of it at 12% and part at 11%. the total yield was $133.75. How much was invested at each rate?

first one:
let the amount invested at 9% be x
let the amount invested at 10% be 15000x
.09x + .10(15000x) = 1432
multiply each term by 100
9x + 10(15000x) = 143200
x = 6800
x = 6800
so $6800 were invested at 9% and $8200 at 10%
do the second question the same way. 
90+10(15000x)=1432000