Solve the proportions.

a) [[$ \displaystyle\frac {x} {3} = \displaystyle\frac {2} {1} $]]



x =

b) [[$ \displaystyle\frac {20} {4} = \displaystyle\frac {x} {6} $]]



x =

c) [[$ \displaystyle\frac {x} {8} = \displaystyle\frac {1} {2} $]]



x =