How can you recognize whether a real-world situation should be represented by an equation or an inequality?

You have to listen carefully to the words.

When the situation is described, if the description says that
one amount 'IS' the other amount, or 'is equal to' the other
amount, or 'is the same as' the other amount, that's your
cue to use an equation.

But if you hear any of the phrases on this list, then it's asking
for an inequality:

-- ' more than '
-- ' bigger than '
-- ' less than '
-- ' smaller than '
-- ' not more than '
-- ' not less than '
-- ' at least '
-- ' the most '