I think if you take the two of the equations and subtract them from eachother then youll get a number being x=(blank) then just subsitute it in for the third equation and see if it works. (sorry if this doesnt help)
She would save 54.45 because addding them up individually before the plan would cost 184.49 and to find the difference all you have to do is subtract 184.49-129.99 and that would tell you how much she saved