Problem with applying matrices to common questions

Question

A person invested $72007200 for 1 year, part at 44%, part at 1111%, and the remainder at 1313%. The total annual income from these investments was $775775. The amount of money invested at 1313% was $200200 more than the amounts invested at 44% and 1111% combined. Find the amount invested at each rate.

Answer 1

Similar to your other question. Total amount (7200) divided into 3 x, y and z, invested x bat 4% y at 11% and z at 13%. So

 

x+y+z=7200 (Total  amount)

0.04x+0.11y+0.13z=775 (Total income)

x+y+200=z 

Thus, we have

x+y+z=7200
4x+11y+13z=775 00
x+y-z=-200

The answer should be

x=1300, y=2200, z =3700