Simply the following:
5.1 ½ + 3⅔
5.2 7 + 3⅔
5.3⅔×⅚
5.4 0,9 x 0,3
5.5 84 - 0,7
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The first one, i believe, would be correct. all the others have one thing in common, and that's that they have repeating numbers. in the second one, x and y have repeating 6's and 3's, and in the third, x and y have repeating 6's as well. in the last one, there are repeating 3's. the first one has no repeating numbers.

I’m not sure what sujevtbis this