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, a portion earning a simple interest rate

Phyllis invested dollars, a portion earning a simple interest rate of percent per year and the rest earning a rate of percent per year. After one year the total interest earned on these investments was dollars. How much money did she invest at each rate?

At rate percent 4

At rate percent 7

Treena,

You need to include numbers of dollars.  You did include the rates.

Phyllis invested A dollars, a portion earning simple interest rate 4% and the rest earning  7% (is this 7% simple or compound?).   After one year the total interest earned was \$C.  how much did she invest at each rate?

Let's assume both interest rates are simple interest rates.   Phyllis ended up with C dollars.   I assume C dollars is greater then A dollars.   So your equations are:

A = D + E where D dollars was invested at 4% and E dollars at 7%, and
C = D(1.04) + E(1.07) since D dollars was invested at 4% and E dollars was invested at 7% and after one year you end up with (dollars)(1+interest rate) dollars.

Now you have two equations in two unknowns and so it's possible to find a solution.   But you need to provide the numbers A and C.

Treena, your question does not contain enough information (i.e.- initial investment dollars, or total interest earned). No answer can be derived without additional information.