Answer:
195 single rooms and 120 double rooms
Step-by-step explanation:
Given
Represent the single room with S and the double with D.
[tex]S = 75 + D[/tex] --- 75 more single rooms
[tex]S + D = 315[/tex] --- Total number of rooms
Required
Find the number of each room
Substitute 75 + D for S in [tex]S + D = 315[/tex]
[tex]75 + D + D = 315[/tex]
[tex]75 + 2D = 315[/tex]
Collect Like Terms
[tex]2D = 315 - 75[/tex]
[tex]2D = 240[/tex]
Make D the subject
[tex]D = \frac{240}{2}[/tex]
[tex]D = 120[/tex]
Substitute 120 for D in [tex]S = 75 + D[/tex]
[tex]S = 75 + 120[/tex]
[tex]S = 195[/tex]