a.4/5-2/3+1/5-1/3
=(4/5+1/5)-(2/3+1/3)
=5/5-3/3
=1-1
=0
b.2/5×7/4-2/5×3/7
=2/5×(7/4-3/7)
=2/5×37/28
=37/70
c.13/4×2/3×4/13×3/2
=(13/4×4/13)×(2/3×3/2)
=1×1
=1
d.2/3×3/4×4/5×5/6
=2/6
e.2/5+6/9+3/4+3/5+1/3+1/4
=(2/5+3/5)+(6/9+1/3)+(3/4+1/4)
=5/5+9/9+4/4
=1+1+1
=3
f.75/100+18/21+19/32+1/4+3/21+13/32
=(75/100+1/4)+(3/21+18/21)+(19/32+13/32)
=100/100+21/21+32/32
=1+1+1
=3.