[tex]x \div y = 3 \div 5 \\ it \: means = \\ 3y = 5x \\ x - y = 18 \\ [/tex]
To solve we multiply the last equation by 5 and we get the following:
5x-5y=90
But 5x=3y and we replace it in this equation:
3y-5y=90
-2y=90
y=-45
and x-(-45)=18 , x+45=18
x=-27
