4. In 1936 my real father wrote a book about how I could be made to work as a “universal machine” to ______ (解决) any difficult sums.

solve vt. 解答；解决(疑惑；困难；问题)

solution n. a solution to sth … 的解决方法

the answer/key/entrance to

Settle?

平息；解决(争议；争端；)

solve a mystery/puzzle/difficulties/problem

settle a quarrel/dispute

solve