21. 5×(3/4×16/24)=
=5×(3/4×2/3)=
=5×1/2=5/2
22. 1 1/2× 1 1/3=
=3/2×4/3=2
23. 22/27×1/3×81/11=
=22/81×81/11=2
24. 6/31×(2 1/5-1 1/6)=
=6/31×(11/5-7/6)=
=6/31×(66/30-35/30)=
=6/31×31/30=1/5
25. 2,7:10=0,27
