## Getting a number from interest equation [closed]

Here is the question for my homework:

A mother wants to invest 7000 USD for her son's future education. She invests a portion of the money in a bank certificate of deposit (CD account) which earns 4% and the remainder in a savings bond that earns 7%. If the total interest earned after one year is \$420.00, how much money was invested in the CD account?

Now, here is my steps:

Amount invested in the savings bond can be represented as 7000 - x

The interest earned in one year on the CD account is 0.04x

So, the interest earned on the savings bond in one year can be represented as: 0.07(7000-x)

The total interested earned after one year is 420.00 USD

The equation is now 0.04x+0.07(7000-x) = 420.00

Now to SIMPLFY it.

I have this so far

n - 420.00 = 0.03x

How do I get the number N?

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 MO is for questions of interest to research mathematicians. Try posting it at one of the sites listed in the FAQ, like math.stackexchange.com – Alberto GarcĂ­a-Raboso Oct 3 2010 at 20:23