Question 44704
no, you don't have to multiple because the equation doesn't have fractions.
You would try to move 2 of the varables to the right and work with2 of the variables.
6x=4y-5x+31
2y=-5x-2z+13
y=(-5x-2z+13)/2  
Now put the above equation into each of the other 2 equations left and then work just with x and z (it will be just a 2 variable equation after that)