SOLUTION: Hello, I need help on two problems using the substitution method; The solution to the system of equation below is (8,4) 3x-5y 7x + 3y = 68 The second problem is: Bill

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Question 440728: Hello,
I need help on two problems using the substitution method;
The solution to the system of equation below is (8,4)
3x-5y
7x + 3y = 68
The second problem is:
Bill invested some money at 5% annual interest, and Jeanette invested some at 7%. If their combined interest was $310 on a total investment of $5,000, how much did Bill invest?
Thanks in advance
Answer by mananth(16949) About Me  (Show Source):
You can put this solution on YOUR website!
Bill 5.00% per annum
Jeanette 7.00% per annum

x+y=5000 ------------------------1
5.00%x+7.00%y=$310.00
Multiply by 100
5x+7y=$31,000.00 --------2

Multiply (1) by -5
we get

-5x-5y= -25000.00

Add this to (2)

2y=$6,000.00

divide by 2

y= $3,000.00 investment at 7.00%---- Jeanette
Balance $2,000.00 investment at 5.00% --- Bill