7. (10 points) Households A, B, and C plan to subscribe to newspapers, with 5 different newspapers available for selection. It is known that each household subscribes to two different newspapers, and any two households have exactly one newspaper in common. How many different subscription methods are there for the three households?
【Solution】Solution: According to the problem, there are two different subscription types: $a b, a c, a d$ and $a b, a c, b c$. For $a b, a c, a d$, there are $C_{5}^{1} \times \dot{A}_{4}^{3}=5 \times(4 \times 3 \times 2)=5 \times 24=120$ ways; for $a b, a c, b c$, there are $C_{5}^{3} \times C_{3}^{3}=10 \times 6=60$ ways.

Therefore, there are a total of $120+60=180$ different subscription methods.