Thanks, however I was more interested in finding out how to present any solution, rather than an answer to this particular problem.
Just for information my attempt was as follows:
12m x 5b = 60m (a)
20m x 3b = 60m (b)
2b = 60 implies_symbol 1b = 30m
1/12m - 1/20 = 5/60m - 3/60m = 2/60m = 1/30m
Therefore_symbol 1/30b in a minute implies_symbol 1/30b x 30 = 1b Therefore_symbol 30 minutes.
m stands for minutes
b stands for bath tubs
Apologies, don't know how to insert symbols into post.
Any links which talk about how to present equations, working, formulae, proofs or whatever they maybe called will be appreciated.