a)ab=10,12,14,16,18 20,24,26,28,30,32,34,36,38,40,42,46,48,50,52,54,56,58,60,62,64,68,70,72,74,76,78,80,82,84,86,90,92,94,96,98.
b) a×b=18 =>2×9=18
3×6=18
6×3=18
9×2=18
=>ab=29,36,63,92
c)a+b=7=>1+6=7
2+5=7
3+4=7
4+3=7
5+2=7
6+1=7
7+0=7
=>ab=16,25,34,43,52,61