[tex]\frac{1}{3}x=\frac{1}{4}x-10\\ x+y=285\\ \left \{ {{\frac{1}{3}x=\frac{1}{4}x-10} \atop {x=285-y}} \right. \\\frac{1}{3}(285-y)=\frac{1}{4} y-10\\ 285-y=\frac{3}{4}y-30\\ 1140-4y=3y-120\\-4y-3y=-120-1140\\-7y=-1260\\y=180\\x=285-180\\x=105[/tex]