We know that
LCM
= Number which gives remainder 0 when dividing by 2, 4, 6
Since LCM gives remainder 0
LCM + 7 will give remainder 0
So, Required Number = LCM + 7
LCM of 2, 4, 6 = 12
Required Number = LCM + 7
= 12 + 7
= 19
Same concept is used in Example 14 and Ex 3.7.4