2/5*7.6+0.4*0.4
=0.4*7.6+0.4*0.4
=0.4*(7.6+0.4)
=0.4*8
=3.2
9.75-5/7+1/4-2/7
=(9.75+1/4)-(5/7+2/7)
=10-1
=9
4/9[3/4-(7/16-0.25)]
=4/9*[3/4-7/16+0.25]
=4/9*[3/4+1/4-7/16]
=4/9*[1-7/16]
=4/9*9/16
=1/4
16*2/3*(9*1/8)
=16*2/3*9*1/8
=(16*1/8)*(2/3*9)
=2*6
=12