Explanation:
Let S be the sample space 
S={HH, HT, TH, TT}
n(S)= 4
A: both the coins with some place
B: both the coins with different place 
C:at least one tail
D:at the most one head 
1) A={TT,HH}
n(A)=2
P(G)= n(A)/n(S)
 = 2/4
 = 1/2
2) B ={HT, TH}
 n(B) = 2
 P(B) = n(B)/n(S)
 = 2/4
 = 1/2
3) C= {HT, TH, TT}
 n(C)=3
P(C) = n(C)/n(S)
 = 3/4
 4). D={HT, TH} 
 n(D) = 2
 P(D) = n(D)/n(S)
 = 2/4
 =1/2