How to get answer?

Question

3. Walt made an extra $9000 last year from a part-time job. He invested part of the money at 9% and the rest at 8%. He made a total of $770 in interest. How much was invested at 8%?

Answer 1

You need to make 2 separate equations.

n + x= 9000

which is going to be the money invested...

then write .08n + .09x= 770

then sove for either n or x in the 1st equation, im going to solve for x, but it could just as easily be n

x= 9000-n

then substitute x in the second equation with 9000-n

.08n+.09(9000-n)=770

.08n+ 810-.09n=770

-.01n=-40

n=4000

So 4000 is invested at 8 percent, and 5000 was invested at 9

Answer 2

Start with this equation:

9000 x Pct x 0.09 + 9000 x (1 - Pct) x 0.08 = 770

solve for Pct

Pct = 0.55555556

Answer: invest 55.56% of $ 9,000 at 9% and invest 44.44% at 8% and you make $770 in interest.