Fill in 1 / 2, 1 / 3, 1 / 6 in each formula to make the equation hold. (fraction + fraction) / fraction = 1

Fill in 1 / 2, 1 / 3, 1 / 6 in each formula to make the equation hold. (fraction + fraction) / fraction = 1

First, divide the copies into 3 / 6 (1 / 2), 2 / 6 (1 / 3) and 1 / 6
Then the formula is (1 / 3 + 1 / 6) / (1 / 2) = 1