In an hour she can sew 16/21 dress.
1) We need to dived those dresses in hours.
2) 4/7 ÷ 3/4
3) 4/7 × 4/3 (explanaintion) >>> Do Keep, Change and Flip. You keep the fraction 4/7, change the (÷) sign to (×) since you need to change the sign, then you flip the fraction 3/4 and get 4/3
4) 4/7 × 4/3 = 16/21
5) So in one hour she can make 16/21 dress.
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And have a nice day! :)
