Find each expression mentally show the steps you used 5x39

Well i'm not sure what the perfect explanation to this answer is but you just multiply 39x5 so 5x9+5x3

I'm not sure if this is how your teacher wants you to do mental multiplication, but these are a couple of ways I would do it.

1.  This is probably the "better" way -- notice that 5 * 39 is just like (5 * 40) - 5.  From here:

(5 * 40) - 5
200 - 5
195

2.  Another method you could use would be to divide 39 by 2 then multiply by 10.  It works mainly because dividing by 2 is multiplying by 0.5.  Then, multiplying by 10 moves the decimal over to the right.  It's like breaking up the * 5.  It would go like this:

(39 ÷ 2) * 10
19.5  * 10
195

I provided two methods of solving, but either way, the solution is 195.