9. if y varies directly as x and y=3 when x=7, find x when y=15 10. if y varies directly as x and y=16 when x=48, find x when y=15
11.two quantities ,x and y, vary directly, if x=12 and y=8, find x when y =28.
12.two quantities ,x and y, vary directly, if x=49 and y=35, find x when y =10.