The 3 guys have now actually paid 90 cents each. So, 3x90 = 270 cents.
The fourth guy kept 20 cents because the bread only costs 250cents.
20+250=270 -> that's what the three had paid.
No 10 cent for me left
The 3 guys have now actually paid 90 cents each. So, 3x90 = 270 cents. 270 + 20(what the fourth guy keeped) = 290 .... that's nonsense.
3x90(what the three paid for the bread)-20(fourth man)-250(Bread)=0