A man invests a portion of $3600 at 8% annual interest and the balance at 7%. If he receives $264 interest during the first year, how much did he invest at each rate?

Question

I would like to know how to work it out correctly 

Answer 1

Let x=amount invested at 8% then 3600-x was invested at 7%.

Interest after 1 year is 0.08x+0.07(3600-x)=0.01x+252 and this comes to 264.

So 0.01x=264-252=12. Multiply through by 100: x=1200 so 3600-1200=2400.

$1200 invested at 8% and $2400 at 7%.