If 1 1 1 1 = R 2 2 2 2 = T 3 3 3 3 = E 4 4 4 4 = N Then 5 5 5 5 = ?

If you add all the terms of the LHS of equality, then the last letter of the sum written in words would give you the RHS.

1 + 1 + 1 + 1 = 4 = FOUR

2 + 2 + 2 + 2 = 8 = EIGHT

3 + 3 + 3 + 3 = 12 = TWELVE

4 + 4 + 4 + 4 = 16 = SIXTEEN

So, following the same pattern.

5 + 5 + 5 + 5 = 20 = TWENTY

That gives us our answer to 5 5 5 5 =  "Y".