Which of the equations are rational equations?

a) [[$ \displaystyle\frac {x + 1} {5} = \displaystyle\frac {1} {2} $]]

Answer: The equation is is not a rational equation.

b) [[$ \displaystyle\frac {x + 1} {x} = \displaystyle\frac {x} {3} $]]

Answer: The equation is is not a rational equation.

c) [[$ \displaystyle\frac {4} {x + 1} = 6 $]]

Answer: The equation is is not a rational equation.

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

Answer: The equation is is not a rational equation.