
Andy C. answered 09/15/17
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Let X be the amount borrowed from the bank and Y be the amount borrowed from the life insurance.
X + Y = 100000 <---- he borrowed $100k
0.10X + 0.14Y = 12200 <--- 10% = 0.10 and 14% = 0.14; The total interest is $12.2 k
Solving the first equation for Y and multiplying the second equation by 100 to clear the decimals:
Y = 100000 - X
10X + 14Y = 1220000
Plugging the first equation into the second:
10X + 14( 100000 - X) = 1220000
10X + 1400000 - 14X = 1220000 <---- distributive property
0 = 14X - 10X + 1220000 - 1400000 <--- moves everything to right side, signs change; like to keep coefficient positive
0 = 4X -180000 <--- combines like terms
180000 = 4x <---- solves for X
180000/4 = X <--- adds 180000 to both sides; then divides by 4
X = 45000
Y = 100000 - 45000 = 55000
CHECK: 45000 x 10% + 55000 x 14% = 45000 x 0.10 + 55000 x 0.14 = 12200
He borrowed 45000 from the bank and 55000 from the insurance.
The answers are checked, verified, and proven to be correct