Răspuns :
2,5=25/10=5/2
3,5=35/10=7/2
(x-5/2)/7/2=x/4
4*(x-5/2)=7/2*x
4x-10=7/2x
4x-7/2x=10 amplificam pe 4x cu 2
8/2x-7/2x=10
1/2x=10
x=10*2
x=20
3,5=35/10=7/2
(x-5/2)/7/2=x/4
4*(x-5/2)=7/2*x
4x-10=7/2x
4x-7/2x=10 amplificam pe 4x cu 2
8/2x-7/2x=10
1/2x=10
x=10*2
x=20