line 1...roy +(alex/3)=alex+70, or 3r +a=3a+210 . . . line 2...roy +(alex/5)=alex+10 , or 5r +a=5a+50. . . line 1...3r=2a+210, or r=(2/3)a+70 . . . line 2...5r=4a+50 . . . 5*(2/3)a +350=4a+50 . . . (10/3)a -4a=50 -350=-300 . . . 10a-12a=-900 . . . -2a=-900 . . . a=450 . . . r=(2/3)a+70=(2/3)*450+70=370