6 out of 7 plus 2 out of 9 minus 4 out of 21

6 out of 7 plus 2 out of 9 minus 4 out of 21

6 out of 7 plus 2 out of 9 minus 1 out of 21
=54 out of 63 + 14 out of 63-12 out of 63
=56 out of 63
=8 out of 9