<span>5 4/7 : 1 5/21 - (5 2/15 х 3/22 + 1 14/15) =1 13/15
</span>
<span>5 4/7 : 1 5/21=39/7*21/26=9/2
5 2/15*3/22=77/15*3/22=7/10
7/10+ 1 14/15=7/10+29/15=(21+58)/30=79/30
9/2-79/30=(135-79)/30=56/30=1 26/30=1 13/15
</span>
3 микросекунды.наверно так