Linear Inequalities — O/L Mathematics

So much of real life is not "exactly equal to" — it is "at least", "no more than", "under the limit". You must be 18 or older to vote, a bus fare box needs at least the correct coins, your monthly spending must stay below your income, and a safe temperature must stay under 40°C. Equations answer "what is the one value?"; inequalities answer "what is the whole range of values that work?" — and that is the more honest question most of the time.