SOLUTION: 3. One year ago Walt invested $12,000. He invested part of the money at 7% and the rest at 9%. He made a total of $970 in interest. How much was invested at 7%? I tried to figure

Question 199080: 3. One year ago Walt invested $12,000. He invested part of the money at 7% and the rest at 9%. He made a total of $970 in interest. How much was invested at 7%?
I tried to figure this out and I need a hand with this problem
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
Let x=Amount he invested at 7% and y=Amount he invested at 9%

Since he has a total of $12,000, this means that

Also, since he invested some at 7% and the rest at 9%, and received $970, this tells us that

Multiply both sides by 100 to make every number whole.

So we have the system of equations:

Multiply the both sides of the first equation by -7.

Distribute and multiply.

So we have the new system of equations:

Now add the equations together. You can do this by simply adding the two left sides and the two right sides separately like this:

Group like terms.

Combine like terms.

Simplify.

Divide both sides by to isolate .

Reduce.

------------------------------------------------------------------

Now go back to the first equation.

Plug in .

Multiply.

Add to both sides.

Combine like terms on the right side.

Divide both sides by to isolate .

Reduce.

So our answers are and .

This means that he invested $5,500 at 7% and $6,500 at 9%

RELATED QUESTIONS
One year ago Walt invested $12,000. He invested part of the money at 7% and the rest at... (answered by checkley77)

One year ago Walt invested $12,000. He invested part of the money at 7% and the rest at... (answered by RAY100)

3. Walt made an extra $12,000 last year from a part-time job. He invested part of the... (answered by Earlsdon)

3. Walt made an extra $12,000 last year from a part-time job. He invested part of the... (answered by josmiceli)

Walt made an extra $12,000 last year from a part-time job. He invested part of the money (answered by Mathtut)

Walt made an extra $12,000 last year from a part time job. He invested part of the money (answered by MissionPossible)

Walt made an extra $12,000 last year from a part-time job. He invested part of the money... (answered by checkley77)

Could someone help me with this one? I have trouble with word problems. You are greatly... (answered by rfer)

One year ago Walt invested $12000. He invested part of the money at 7% and the rest at... (answered by checkley75,jim_thompson5910)