G= Garrett and L= Liz
Putting words into symbols
G= 3L-1, G+L= $179
For the first equation 3 times L goes first because you want your number to be positive. Putting 1 first would make your number negative. This is how much money Garret has with respect to LIz.
For the second equation you are adding their total amount. Together is their total.
With these two equations you can solve either by substitution or elimination. If you need further assistance, please let me know. This is just the setup to get the answer