在“探究求合力的方法”的实验中

The young man is very brave, he often fights ____ the bad man.  

      Mr. and Mrs. White had two sons and three daughters. One Sunday, Mrs. White said to her husband. The children don' t have any lessons today, and you're free too. There's a new funfair（游乐场） in the park. Let's all go there to play.
     Her husband said, "I want to finish some work today." "Oh, I forget it. Go there and make our children happy. That's the most important work." Mrs. White said.
     So Mr. and Mrs. White took their children to the funfair. Mr. White was forty-five years old but he enjoyed the funfair more than his children. He hurried from one thing to another, and ate lots of sweets. One of the children said to her mother, "Dad is just like a small child, isn't he, Mom?" Mrs. White didn't want to follow her husband around any more at that time and answered, "He is even worse than a small child, Mary, because he might spend（花费）more money than a small child."

先化简，再求值： ，其中.