YOU SAID:

i ate my maths book for fun

INTO JAPANESE

私は楽しみのために私の数学の本を食べました

BACK INTO ENGLISH

I ate my math book for fun

INTO JAPANESE

数学の本を楽しみに食べました

BACK INTO ENGLISH

I was looking forward to eating a math book

INTO JAPANESE

数学の本を食べるのが楽しみでした

BACK INTO ENGLISH

I was looking forward to eating a math book