Susan invests

3

times as much money at

11

%

as she does at

7%

. If her total interest after

1

year is

$2000

, how much does she have invested at each rate?

Let's say she invested at 7% "a" amount

now, she invested at 11% three times as much, so 3*a or "3a"

how much is 7% of a? well, (7/100) * a or 0.07a

how much is 11% of 3a? well (11/100) * 3a or 0.11 (3a)

now, we know her total yield in interest is 2000 bucks, so whatever 0.07a is and 0.11 (3a) are, they add up to 2000

0.07a + 0.11 (3a) = 2000

solve for "a".