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Explanation:
The fractions 2/3, 1/6 and 1/9 have the denominators 3, 6 and 9. The LCM is 18, so the LCD of the fractions is 18.
2/3 = 12/18 after multiplying top and bottom by 6
1/6 = 3/18 after multiplying top and bottom by 3
1/9 = 2/18 after multiplying top and bottom by 2
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The three original fractions 2/3, 1/6, and 1/9 are equivalent to 12/18, 3/18, and 2/18 in that exact order.
With the fractions all having the same denominator, we can add the numerators to place over the common denominator
12/18 + 3/18 + 2/18 = (12+3+2)/18 = 17/18
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After combining all of the shaded areas, we have 17/18 of the circle shaded in with 1/18 of the circle not shaded in.
You subtract 17/18 from 1 to get 1/18
1 - (17/18) = 18/18 - 17/18 = (18-17)/18 = 1/18
You could think of it like having 18 slices of cake total, and 17 are eaten by guests, so 18-17 = 1 is left over out of the 18 overall. So 1/18 of the cake hasn't been eaten.
