Step-by-step answer:
For relatively small denominators, the easiest way is to multiply the two denominators AND divide by the highest common factor (HCF).
For example, adding 5/24+3/16
24*16 = 384
(use a calculator if necessary, for mental calculation, 24*16=20^2-4^2=400-16=384 ).
The highest common factor (HCF) is 8, since 24/8=3, 16/8=2, 3 and 2 do not have any more common factors, so it is the HCF.
The lowest common multiple (LCM) is then 384/8 = 48
For someone good at factoring, we see that the factors are:
24={2^3,3}
16={2^4} = {2^3,2}
so the LCM is either 16*3=48, or 24*2=48.
