Answer:
She invested 1600 at 8% (to get the shown $160 interest)
and $7400 at 10% (to get the shown 640 interest)
If x = 4000 then $80 interest is x2 again = $160
and so forth $320 interest x 2 again = $640
Step-by-step explanation:
The format would always be for x and then where
investment - x = interest we can work out totals this way and find x.
9000-x = 800 is first equation and substituted into 2nd equation;
0.10x+0.08(9000−x)=800
Use the distributive property to multiply 0.08 by 9000−x.
0.10x+720−0.08x=800
Combine 0.10x and -0.08x to get 0.02x.
0.02x + 720 = 800
Subtract 720 from both sides.
0.02x=800−720
Subtract 720 from 800 to get 80.
0.02x=80
Divide both sides by 0.02.
x= 80 / 0.02
Make decimals numbers = 1 or above.
80 / 0.02 x 100
x= 8000 / 2
x = 4000
