Here is how I make 21 with 1, 5, 6, and 7 Comment 6 / (1 - 5 / 7) = 6 / (2 / 7) = 6 * (7 / 2) = 21 Reply
6 / (1 - 5 / 7)
= 6 / (2 / 7)
= 6 * (7 / 2)
= 21