Answer:
5x+2x
Step-by-step explanation
Considering you will buy the same amount of rulers and notebooks, x will represent the same number.
Since you will buy an x number of notebooks that cost $5, 5x, and an x number of rulers that cost $2, 2x, you can combine them to make 5x+2x.
Use
To use the expression you can fill in any number for x.
Imagine you have 30 students, you could replace each x in the expression with 30. This would give you 5(30) + 2(30).
Multiplying each would give you 150 + 60 which results in $210.