Solve the proportions.

a) [[$ \displaystyle\frac {2} {a} = \displaystyle\frac {3} {8} $]]



[[$ x = $]]

b) [[$ \displaystyle\frac {100} {5} = \displaystyle\frac {b} {2} $]]



[[$ x = $]]

c) [[$ \displaystyle\frac {c} {9} = \displaystyle\frac {3} {1} $]]



[[$ x = $]]

d) [[$ \displaystyle\frac {11} {2} = \displaystyle\frac {66} {d} $]]



[[$ x = $]]