In your assessment or capacity test, Basic Arithmetic tests how well and how quickly you can solve mathematical exercises. Your knowledge of the most commonly used mathematical operations is tested with questions about equations with one unknown variable. The tasks are generally not complicated, but in an assessment you will need to solve many exercises in a relatively short time. So it is good to practice a lot.
If it has been a long time since you have made calculations, it is useful to look at the examples in which the basic calculation rules explained, including explanations.