Answer:
A 5040
B 35
Step-by-step explanation:
A There are 7 ways to put the first picture. There are 6 pictures left and 6 ways to put the 2nd picture. There are now 5 pictures left and 5 ways to put the 3rd picture. And so on
7 * 6*5*4*3*2*1
5040
B If we can only have 3 pictures and order does not matter
7 choices for the first * 6 *5
But
We have to take into account order
The first picture can go into 3 slots, the second into 2 and the third 1 so divide by 6
(7*6*5)/ (3*2*1)
35