suppose Julia had M money at the beginning, let T is the price for each t-shirt , we will have
M-8T=-28 (1) M-4T-15=17 (2). {15 is the value for the 3 hats x $5 each} the (2) becomes M-4T=32 (3)
subtracting the (1) from (3) we get 4T=60 so T = 60/4 and T = 15
Now adding (1) and (3) we get 2M - 12T = 4 , plugging the value of T we have 2M - 180 = 4 --->>>
2M = 184 and M = 184/2 so M = 92 this is the money Julia had at the beginning $92.