Turn a word problem into an equation by identifying the requested quantity, reference value and measurement units.
Write down what the question asks for, including its unit. A price after discount, a discount amount and a discount percentage are three different outputs. List the known values separately before choosing an operation.
A price rises from 80 to 100. The increase is 20, and the reference for percentage increase is 80, giving 25%. Comparing that same 20 with the final price gives 20%, which answers a different question.
If three identical items and a 6-unit delivery charge cost 42, write 3x + 6 = 42. Subtract delivery first: 3x = 36, so x = 12. Check by substitution: 3 × 12 + 6 = 42.
Distance divided by speed has units km / (km/h) = h, so it produces time. Distance multiplied by speed does not. Convert minutes to hours or centimetres to metres before combining quantities. Keep intermediate precision and round at the end.
English edition: 16 September 2026.