Question 533674
Let 
Lisa spent = l
Fred Spent = f


lisa and fred spent 15.30
l+f=15.30.........(1)


lisa spent 3.50 more than fred
l = f + 3.50.........(2)


Put the value of l in (1)
f+3.50+f=15.30
2f=15.30-3.50
2f=11.80
f=11.80/2
f=5.90
Plug in the value of f in (2)
l = f + 3.50
l = 5.90 + 3.50
l = 9.4


Lisa spent = l = 9.4
Fred Spent = f = 5.90