Understanding numbers is important for solving math problems.

He was bedridden with illness for several days.

I can't solve this problem because there are too many numbers.

The use of mobile phones is prohibited during class.

There is a class observation at my son's school tomorrow.

This reaction occurs through a chemical process.

He is an excellent chemist who made many discoveries.

He is an expert in petrochemistry.

It's difficult to decipher this chemical equation.

Understanding chemical equations is difficult.