Pushpa K. answered • 04/03/16

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Sung invested $ 20,000 in two accounts. Let one account be x, another account be y.

x + y = 20,000 --------------- Equation 1

One account paid 10% interest and another paid 6%. Total interest received was $1400

0.1 x + 0.06 y = 1400 -------------Equation 2.

Now there are two variables in two equations that can be solved by substitution or by elimination method.

To solve by substitution, first isolate x in the first equation by subtracting y on both sides.

x + y = 20,000

x + y - y = 20,000 - y

x = 20,000 - y

Now substitute x = 20,000 - y into equation 2.

0.1 x + 0.06 y = 1400

0.1 ( 20,000 - y ) + 0.06 y = 1400 --------------- Distribute and combine like terms

2000 - 0.1 y + 0.06 y = 1400

- 0.04 y = - 600 ---------- subtract both sides by - 0.04

- 0.04 y/ -0.04 = -600/ -0.04

y = 15,000

Substitute y = 15,000 in to equation 1 and solve for x.

x + y = 20,000

x + 15,000 = 20,000

x = 5000.

$5,000 was invested at 10% and $15,000 was invested at 6%.