Răspuns :
21 =3 x / 100
3 x =21 *100
3 x =2100
x =2100 :3
x =700 verificam
21 =3 *700 / 100
21 = 2100 / 100
21 = 21
3 x =21 *100
3 x =2100
x =2100 :3
x =700 verificam
21 =3 *700 / 100
21 = 2100 / 100
21 = 21
35x\100=21 35x=2100(produsul mezilor egal cu produsul exremilor)
x=2100\35
x=60
x=2100\35
x=60