Systems of Equations/Inequalities

1.) Solve the following system of equations using Gaussian elimination:

3w+10x-2y+3z=55

w+12x-11y-z= 69

-3w-6x-5y-10z=-47

-3w+9x+5y+4z=-1

Here's what I did so far:

swap R1 and R2 (row 1 and row 2)

-3R1+R2 (multiply row 1 by -3 and add row 2 to that product)

3R1+R3

3R1+R4

Now, after that I think I may have made a mistake because I eventually get some very odd fractions that could not possibly be correct. Can somebody tell me what the next steps are???

2.) Rachel has 3 investments for a total of $9000. They earn interest at 5%, 7%, and 9%, respectively. The total income is $7100. The income from the 9% investment exceeds the total from the other two investments by $1900. How much money is the investment that earns the 5% interest?

I have absolutely no clue how to write the system for this. Can somebody at least help me get started???

I would really appreciate your help on this! Thank you!!!