a) 2x / 72 este ireductibila=> x/36 este ireductibila=> x ∈{1,5,7,8,10,11,13,14,15,16,17,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,37....
b) 40 minute
4. 5,4=2,7x=>x=5,4: 2,7=2
5. x+13<3x+1 <=>x+12<3x |-x 12<2x=> x∈{3,4,5....}
imi pare rau dar nu stiu 6 si 7