Help counting

If the 2 boys must stand next to each other, you can treat them as one thing. That means there are 4 things to arrange, which is just 4! = 24

The two boys can stand next to each other in 8 ways in the line of 5

  then fill the other three slots with the girls   3 x 2 x 1

 8 x 3 x 2 x 1 = 48 ways

The 2 two boys  can  be arranged in  2 ways   and they can fill any of  4 spots 

And  for each of these, the girls can be arranged in 3! = 6  ways

So

2 * 4 * 6   =    48  ways