Five friends went to a restaurant and agreed to share the bill equally. however, one person forgot his wallet so the other four friends' portions of the bill went up by $4 each. how many dollars was the total bill?

Hey there :)

1 ) Five friends went to a restaurant with an agreement to share the bill
2 ) One forgets so four friends part of bill rose by $4 each

Let p represent the total amount of bill

Translating (1) into mathematics:
      ( Original agreement )

Translating (2) into mathematics:
      ( Share among four )

Portions of bill increases by
4

Therefore, 


Change to same denominators 


p = $80

The total bill was $80

Yes, two vertical lines can be complementary