calculator solving linear eqns in terms of unknown

[yland]

My friends less expensive ti solves a 3x4 system of linear equations in terms of 4th unknown. How do i do this on my prime?

Example
2a+2b+2c=0
3a+b+2c=0
a+b+c=W

I want to get all my variables in terms of W. The type of problem im solving is a statics problem and im asked to find the maximum weight of flowerpot if the chain can hold a max 50lb tension. So W represents the maximum weight (flowerpot) that the system can hold. How do i input this?