Let the portion that earns 4% equal x 4%=.04

Let the portion that earns 7% equal 9000-x 7%=.07

then

.04(x)+.07(9000-x)=540

.04x+630-.07x=540

630-.03x=540

-.03x=-90

x=90/.03=90*100/3=9000/3=$3000

solve for x. X will give you the amount of money in the cd account

so….

.04x+.07(9,000-x) = 540

(solve for x)

So .07 times 9000

then .07 times -x

combine like terms, with the .04x.

Subtract whatever .07 times 9000 came out to be from both sides

-divide by (-x)….. this is the amount invested at 4%. To fine the amoutn at 7%, plug in x into the equation: .07(9,000-x) =amount invest at 7%.

Hope this helps 🙂

x+y=9000

.04x+.07y=540

.04x+.04y=360

.04x+.07y=540

–subtract them–

-.03y=-180

y=6000

x+6000=9000

x=3000

so x=3000 & y=6000

hope this helped!