Answer:
72
Explanation:
For now, let's just distinguish between boys and girls.
Boy = X
Girl = x
There are 6 ways of placing the boys and girls so that the girls are not next to each other.
XXxXx
XxXXx
xXXXx
XxXxX
xXXxX
xXxXX
Now let's look at one of those patterns while distinguishing between the individual boys and girls by having a different symbol for each.
Boys: A, B, C
Girls: a, b
Let's use just the first pattern above, XXxXx.
ABaCb
ACaBb
BAaCb
BCaAb
CAaBb
CBaAb
ABbCa
ACbBa
BAbCa
BCbAa
CAbBa
CBbAa
For the first pattern of the 6 different patterns on top, there are 12 ways of placing the boys ad girls. Since there are 6 of the patterns on top, the total number of ways is
6 * 12 = 72
Answer: 72