[tex]a)11,20.[/tex]
[tex]1 + 1 = 2[/tex]
[tex]2 + 0 = 2[/tex]
[tex]b)13,22,31,40.[/tex]
[tex]1 + 3 = 4[/tex]
[tex]2 + 2 = 4[/tex]
[tex]3 + 1 = 4[/tex]
[tex]4 + 0 = 4[/tex]
[tex]c)15,24,33,42,51,60.[/tex]
[tex]1 + 5 = 6[/tex]
[tex]2 + 4 = 6[/tex]
[tex]3 + 3 = 6[/tex]
[tex]4 + 2 = 6[/tex]
[tex]5 + 1 = 6[/tex]
[tex]6 + 0 = 6[/tex]
[tex]d)17,26,35,44,53,62,71,80.[/tex]
[tex]1 + 7 = 8[/tex]
[tex]2 + 6 = 8[/tex]
[tex]3 + 5 = 8[/tex]
[tex]4 + 4 = 8[/tex]
[tex]5 + 3 = 8[/tex]
[tex]6 + 2 = 8[/tex]
[tex]7 + 1 = 8[/tex]
[tex]8 + 0 = 8[/tex]