Use the digits 1 though 9 once each. Fill in the 3x3 squares to make the sum of 777. Thanks.

Answer 1

if you have 9 squares and 9 digits, that only leaves on digit for each square.

I can't see how to add 3 single-digit numbers to get anything greater than 7+8+9=24.

Is there a trick, or something missing here?

Answer 2

I made the last row negative, so the sum of 235, 689, and -147 = 777. Personally, though, I think it's a mistake since I couldn't get 3 positive numbers to = 777.