Продолжите ряды чисел. 2, 4, 6, ... 5, 10, 15, ... 7, 14, 21, ...

а) ...8, 10, 12; ...20, 25, 30; ...28, 35, 42; ...12. 15, 18;
...24, 30, 36; ...24, 20, 16; ...48, 40, 32; ...54, 45, 36.
б) Самостоятельное задание.