Question 625022
1. Carolyn received a check last week. She invested part at 15%and $1000 more than this at 16%. If she will earn $780 in interest in a year, how much was invested at each rate? 

This is what I have so far:
I=PRT

x= first investment 
x+1000 second investment 
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You can do it that way.
Then,
0.15x + 0.16(x+1000) = 780
0.31x + 160 = 780
x = 2000
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$2000 @ 15%
$3000 @ 16%