When Party A and Party B meet for the first time,
7/(7+11) = 7/18 from A to B.
1118 from b to a.
After the same time.
7/18+7/18 =14/18 from A to B.
B from B to A and then from A to B (118+118)-1= 4/18,
After the same time.
A goes from A to B and then from B to A (14/18+7/18)-1= 3/18.
4/18+118 =15/18 from A to B.
According to the calculation, Party A and Party B meet at this time.
According to the topic, Serie A is 80 kilometers away from B, which is 3/ 18 of the total length.
Ab is 80/(3/ 18) = 480km apart.