I really don't know how to explain this with pictures.. so I'll try to explain it as well as I can. if you don't know your multiplication facts I suggest you get a chart from google or something.
1. Start by stacking the numbers. ex:
125
x 3
2. do 5x3, which is 15. We don't place the 1 with the 5 in the same place. it should look like this:
125
x 3
----------
5
We can save the one for later. Now, we move onto 3x2, which is 6. NOW we bring the one back, and we add it to the answer of 3x2. So 6+1 is 7, so now we put 7. like this:
125
x 3
---------
7 5
Last step! now, we do 1x3 which is 3. Any number times 1 will always be that number. For example, 1x123456789 will always be 123456789 because it is multiplied by one.
your answer should end up looking like this
125
x 3
---------
375
If that was too confusing, maybe you should watch a Mr. J video. Here's the link:
Mr J Multiplication Video