You need to use your head to solve this problem.

He is passionate about researching pure mathematics.

He is majoring in applied mathematics at university.

His smile is so charming that it's irresistible.

He is a world-famous mathematician.

Combinatorics is a branch of mathematics that studies combinations of things.

Combinatorics is a branch of mathematics that studies combinations of things.

Combinatorics is a branch of mathematics dealing with issues of order and choice.

Discrete mathematics is an important field that forms the basis of computer science.

No problem, I will do that job.