Ayearbook page will show 20 photos displyed in rws each row must contain the same number of photos how many different ways can the photos be arranged

Try this solution:
if one row consists of 20 photos and we have 20 photos, then number of ways is:
20*19*18*17*16*15*14*13*12*11*10*9*8*7*6*5*4*3*2*1=20!
or, using formula: A=n!=20!
P.S. 20!=2432902008176640000