SOLUTION: Carmella Santiago earned 42,000 in book royalties. She invested part at 15% simple interest and the rest at 12%, earning 5,790 per year in interest. How much did she invest at each

Question 965166: Carmella Santiago earned 42,000 in book royalties. She invested part at 15% simple interest and the rest at 12%, earning 5,790 per year in interest. How much did she invest at each rate?
I know you have to use I= prt... Right? I just never know how to write it out...
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = amount invested @ 15%
= amount invested @ 12%
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I think they want ( 1 year )
Make this 2 equations:

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Add the equations

Now find and

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