8. (4x+3y)/(7x+9y)=3/8
8(4x+3y)=3(7x+9y)
32x+24y=21x+27y
32x-21x=27y-24y
11x=3y
x/y=3/11
9. a) 5/12+30/25×15/12=
=5/12+6/5×5/4=
=5/12+3/2=
=5/12+18/12=23/12
b) 0,3:1/12=
=3/10:1/12=
=3/10×12=18/5
c) (0,25+3×1/12):2 1/2=
=(1/4+1/4):5/2=
=2/4:5/2=
=1/2:5/2=
=1/2×2/5=1/5
d) 6/13+0,2=
=6/13+1/5=
=30/65+13/65=43/65
