1) a/b= 1,5
b/c= 6/7 fractie ireductibila si b si c sunt cifre, rezulta ca b= 6, c= 7, a= 1,5*6= 9
abc=967
2) (3/4)*a=(2/3)*b /:[(3/4)*]b
a/b= (2/3):(3/4)=(2/3)*(4/3)=8/9
a/b=8/9
a+b=3,4
a= (8/9)*b
(8/9)*b+b= 3,4
17*b= 3,4*9
17*b=30,6
b=30,6:17
b=1,8
a=3,4-1,8
a=1,6
3)
x,y#0 (numere rationale nenule),
2x=3y /+y
2x+y= 3y+y,
2x+y= 4y, y#0, rezulta 2x+y#0
12x-5y= 6*2x-5y= 6*3y-5y= 18y-5y= 13y
2x+y= 4y
(12x-5y)/(2x+y)= 13y/4y= 13/4
