Write a general expression using letters to abstract a general form from the given set of numerical data.
a. 2·3 = 3 + 3
    2·5 = 5 + 5
    2·14 = 14 + 14
    2·27 = 27 + 27

 
b. 2·3 + 2·5 = 2·8
    7·12 + 7·8 = 7·20
    5·40 + 5·2 = 5·42
    3·1 + 3·1 = 3·2