Răspuns :
1. A={14,15,16,17,18,19,20}
B={4,6,8,10,12,14}
A reunit cu B={ 4,6,8,10,12,14,15,16,17,18,19,20}
A intersectat cu B={14}
A -–B={15,16,17,18,19,20}
2. A= 3x<243=> X= 243:3=81
=> mulțimea A= toate numerele de la 0 la 80={0,1,2,....,79,80}
B=5y<125=> y= 125:5=25
=> mulțimea B= toate numerele de la 0 la 24={0,1,2,....,22,23,24}
A reunit cu B= {0,1,2,3,4,....,78,79,80}