a)1/2+2/3:4/9=
=1/2+2/3 × 9/4=
=1/2+3/2=2
b)1/12+4/5:(1/2-1/3)=
=1/12+4/5:[3/6-2/6]
=1/12+4/5:1/6
=1/12+4/5 ×6
=1/12+24/5
=5/60+288/60
=293/60=
=4,88(3)
c) 2:(2/3)²+11/5:11/10=
=2: 4/9+11/5 ×10/11=
=2 ×9/4+2=
=9/2+2=
=(9+4)/2=
=13/2=
=6,5
d) (1/4+7/6)*15/34+3/2*(1/3-1/21)=
=(3/12+14/12)*15/34+3/2*(7/21-1/21)=
=17/12 *