Question

5+5+5=550
????                                           
................................................................?

Answer 1

5 + 5 + 5 = 550
If you add a small line to the plus it will be like:

5 + 5 4 5 = 550
Hence proved.

Answer 2

given us 5+5+5=550??? after added the small line to the plus. we can write this 5+545=550