(1/2+1/3+1/4+1/5) + (1/2+2/3+3/4+4/5)=
numitor comun 120(2x3x4x5=120)
(60+40+30+24)/120+(60+2x40+3x30+4x24)/120=
154/120+(60+80+90+96)/120=
154/120+326/120=
480/120=4
3/5+7/25+2/5+18/15
numitor comun 75(5x5x3)
(15x3+3x7+15x2+5x18)/75=
(45+21+30+90)/75=
186/75
