Going into college and still have no idea how to do this type of question

Question

An apartment building contains 12 units consisting of one- and two-bedroom apartments that rent for $360 and $450 per month, respectively. When all units are rented, the total monthly rental is $4950. What is the number of two-bedroom apartments? Side note- what is the way to solve questions like these?

Answer 1

Using one variable:

x represents the number of one bedrooms

12 - x represents the number of two bedrooms

360x + 450(12 - x) = 4950

Can you solve for x and answer?

 

Using two variables:

x represents the number of one bedrooms

y represents the number of two bedrooms

x + y = 12

360x + 450y = 4950

Can you solve the system?