Rosa invested $8000 for one year, part ast 8% annual interest and the balance at 10% annual interest. Her total interest for the year was $700. How much money did she invest at each rate?

Answer 1

just add up the interest on each part. If $x was at 8%, the rest (8000-x) was at 10%. So,

.08x + .10(8000-x) = 700