How many ways can you arrange 2 boys and 3 girls in a line, if the 2 boys must stand next to each other?
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