Sovling 4 equations with 4 uknowns for equilibrium

[aub]

i know this doesn't fit here right but i didnt know where else i could ask this

Homework Statement

how did they solve 1 through 4? it should be easy but i can't solve it

thanks for any help

 

[phyzguy]

You want to manipulate the equations to eliminate variables. For example, what happens if you add equations (1) and (3) together? Try this and see if you can proceed further.

 

[aub]

ok thanks i solved it