He is good at mathematics.

He took a deep breath, breathed in the fresh air, and showed a relaxed expression.

He is bad at remembering numbers.

Where is my canteen?

The water level of the river has suddenly risen.

This data is showing a significant change over time.

They (referring to women or girls) are my best friends.

He is learning an ancient secret art.

When you multiply the multiplicand and the multiplier, you get the product.

When you divide the dividend by 2, you get the quotient.