It helps immensely if you know your times tables.
a) 36 = 6*6 = 2*3*2*3 = 2^2*3^2
b) 45 = 5*9 = 5*3*3 = 3^2*5
c) 2 is not a common factor; 3^2 is a common factor; 5 is not a common factor. The greatest common factor is 3^2 = 9.
d) The least common multiple can be found a couple of ways.
.. 1) the product of the distinct factors to their highest powers
.. .. .. 2^2 * 3^2 * 5 = 180
.. 2) the product of the numbers divided by their greatest common factor.
.. .. .. 36 * 45 / 9 = 180
