Answer:
129
Explanation:
If you want it reduceable to a unit fraction, then the reciprocal would be equal to an integer. Make an equation, "(333+x)/77=y," and you see the positive side is just under 5, so you plug in "5 = y," and get 52 = x. That isn't a 3 digit number, so you plug in "6 = y," and get 129 = x.