Name a number that can be evenly divided by 6 and and by 7

There are an infinite number of them.  The smallest one is 42,
and every multiple of 42 is another one.

I don't remember the official correct way to solve this problem. 
I can only show you my own way of doing it.

I take the bigger number, and I go through its multiples, one by one,
until I spot one that's also a multiple of the smaller one.

Example:  6 and 7.
Go through the multiples of 7:

7 ... no, not a multiple of 6
14 ... no, not a multiple of 6
21 ... no, not a multiple of 6
28 ... no, not a multiple of 6
35 ... no, not a multiple of 6
42 ... Yes !  A multiple of 6.  yay !

Divide each term in  Y i  =  4  +  1.5 X i  by  i  and simplify.

Y  =  −  4 i  +  1.5 X

Step-by-step explanation: