Question

There are 92 beds in a 40-room motel. Each rooms has 2 or 3 beds. How many rooms have 2 beds?

Answer 1

$x-\ rooms\ with\ 2\ beds\\\\ y-\rooms\ with\ 3\ beds\\\\\\ x+y=40\ \ \ \ --->\ \ \ x=40-y\\ 2x+3y=92\\\\ 2(40-y)+3y=92\\\\ 80-2y+3y=92\\\\ y+80=92\ \ \ | subtract\ 80\\\\ y=12\\\\x=40-12=28\\\\ 28\ rooms\ has\ 2\ beds.$