Answer :

a386
Long division can be tough to get a hang of, but you will definitely need to know how to do it for a lot of math problems.  I've drawn a picture to show how you set it up. 

Now, you take the number you are dividing by (the divisor, 45), and see how many times you can fit it into the number you are dividing (the dividend, 3402).  Easily enough, you can see how many times you can put 45 into the numbers working from the left.
Does 45 go into 3? No.
Move onto the next number.  Does 45 go into 34? No.
Move onto the next number.  Does 45 go into 340?  Yes.

Now this part is tough.  You must find out how many times 45 goes into 340.  You can use trial and error to solve this:
45 x 1 = 45
45 x 2 = 90
45 x 3 = 135
45 x 4 = 180
45 x 5 = 225
45 x 6 = 270
45 x 7 = 315
45 x 8 = 360  This is more than 340, so we know that 45 goes into 340 seven times.

You have to know where to place this seven.  It goes above the line, right above the last number of the number you were dividing, which in this case is the 0 in 340.  Under the 340, you will now write what 45 x 7 equals, 315.  Subtract 315 from 340, and write the result underneath.  It's just like regular subtraction.  I've included another picture to show how to do this.

Now, you will have to go onto the next set of division.  You know 45 doesn't go into 25, so what do you do next? You carry down the 2 from 3402, and put it next to the 25 to make it 252!  Repeat the steps from the first part, and find that 45 goes into 252 five times.  Place the 5 above the 2 on the line, and subtract 225 from 252.  I've included another picture detailing these steps.

You can now see that 45 doesn't divide evenly into 3402.  So, you have to continue into decimals!  Turn 3402 into 3402.0.  This means the same thing, but now you have another number to drop down!  You will get 270, which 45 divides into 6 times evenly.  You will know you have finished solving the problem because you will be left with 0.  Repeat the steps again.  However, when you put a 6 on the line, you must put a decimal point before it.  Otherwise, you would be saying that 756 x 45 = 3402, which definitely isn't true!  I've included one final picture to show you how to do this.

The answer is 75.6
I hope this all made sense!  Keep at it, and you will soon be doing long division like a champ!
View image a386
View image a386
View image a386
View image a386