1) n:5=c rest 1
n:7=c rest 1....=> n=5*7+1...=> n=35+1....=>n=36
36:5=7 rest 1
36:7=5 rest 1
2) n:24=c rest 9
n:18=c rest 9
n:20=c rest 9.....=>n=18*20+9...=> n=360+9...=>n=369
369:24=15 rest 9
369:18=20 rest 9
369:20=18 rest 9
n=369*2-9...=> n=738-9....=> n=729
729:24=30 rest 9
729:18=40 rest 9
729:20=36 rest 9
n=(369 si 729) ...urmatorul nr. care indeplineste conditia este 1089>1000
3) cmmdc(x;y)=2...unde x*y=92...=> x=92:2...=>x=48...=>y=2
cmmdc(48;2)=2