She studied diligently so that she could excel in exams. (simple)

• So that যুক্ত complex কে simple করার নিয়ম:

- প্রদত্ত sentence এর প্রথম থেকে so এর পূর্ব পর্যন্ত বসে,
- so থেকে many/might/can/could পর্যন্ত উঠে যায়,
- to বসে,
- প্রদত্ত sentence এর বাকি অংশ বসে।

Complex: He worked hard so that he could prosper in life.
Simple: He worked hard to prosper in life.

Complex: She studied diligently so that she could excel in exams. 
Simple: She studied diligently to excel in exams. 

Source: Advanced Learners by Choudhury & Hossain.