We'll do it in cents and convert when we have to.
Tanya paid x per item, a total of 4x.
Tony paid x-125 per item (in cents) for a total of 5(x-125)
4x = 5(x-125)
4x = 5x - 625
x = 625 = $6.25
Check:
4(625) = 2500
5(625-125)=2500, same, checks
Answer: Tanya paid $6.25 per item, Tony $5.00 per item