Two items at different profit/loss rates: overall profit equation

CAT has tested this idea 4 times across 4 papers, from 2019 to 2023. Solve one, and the others are the same method with different numbers or wording, which is why repeated concepts are the most efficient thing to practise.

Question	What it asks	Answer
CAT 2020 Slot 1 · QA Q12	desktop at 20% profit, laptop at 10% loss, overall 2%	20000
CAT 2019 Slot 1 · QA Q13	pen and book at two sets of rates; two equations	A
CAT 2019 Slot 2 · QA Q27	six bicycles at 25% profit, four at 25% loss	D
CAT 2023 Slot 1 · QA Q13	two objects sold at the same price, profit and loss	B

Part of Percentages & Profit-Loss (46 questions since 2017).