If y varies directly as x and y = 12 when x = 8, find y when x = 14.

The direct variation between x and y may be written as,
                                    y = kx
where k is the constant of variation. From the first set of values of the variables,
                                 12 = k(8)
the value of k is 1.5. Substituting the next set to the same equation,
                                 y = 1.5(14) 
The value of y is 21. 

First subtract 10 from both side
y^2+6y-16=0
(y+8)(y-2)=0
-8 and 2