未知数多過ぎ
A(H,H)+A(T,T)=0.8
A(H,T)+A(T,H)=0.2
B(H,H)+B(T,T)=0.4
B(H,T)+B(T,H)=0.6

A(H,H)=A(H)*Ah(H)
B(H,H)=B(H)*Bh(H)

P(H,H,H)=？