we know that
the formula for combinations is
nCr=n!/[(n-r)!*r!]
n is the total number of objects
r is the number that you choose to arrange
in this problem
n=5
r=2
C=5!/[(5-2)!*2!]------> C=5!/[(3)!*2!]-----> C=5*4*3!/[3!*2!]
C=20/2----> C=10 ways
the answer is
10 ways