Answer:
a) Somebody was kung-fu fighting for less than 10 hours.
b) All rivers have less than two tributaries.
Step-by-step explanation:
To write minimal negation statements, one must abide by the following rules:
1. If all Xs are Y ⇒ There is one X that is not Y
2. If one X has Y⇒ All Xs do not have Y
a) "Everybody was kung-fu fighting for at least 10 hours"
Following the first rule:
Somebody was kung-fu fighting for less than 10 hours.
b) "There is a river with at least two tributaries"
Following the second rule:
All rivers have less than two tributaries.
