how do i solve? what’s the answer

Question

Jen invested $8000 into two accounts, one paying 5% simple interest and other paying 8%

simple interest. After one year, she made $490 from the two accounts. How much was

invested at each rate?

Answer 1

Let X = amount invested at 5%

Let Y = amount invested at 8%

X + Y = 8000

.05X + .08Y = 490

I will use substitution and rewrite the first equation as

Y = 8000 - X

.05X + .08(8000 -X) = 490

.05X + 640 - .08X = 490

-.03X + 640 = 490

-.03X = -150

X = 5000

Y = 8000 - 5000 = 3000

Checking

.05(5000) + .08(3000) = 490

250 + 240 = 490

490 = 490

$5000 was invested at 5% and $3000 was invested at 8%