Calculate.

a) [[$ \displaystyle\frac {2} {7} + \displaystyle\frac {3} {5} = $]]

b) [[$ \displaystyle\frac {4} {5} + 1 \displaystyle\frac {2} {3} = $]]

c) [[$ \displaystyle\frac {7} {2} - 2 = $]]

d) [[$ \displaystyle\frac {3} {2} - \displaystyle\frac {2} {3} = $]]