can you explain the chart and how to come up with the mathematics

Chapter03.pdf - Adobe Acrobat Reader DC X Chapter04.pdf 32 / 40 72.8% Table 3.1 Illustration of Buying Stock on Margin End-of-Year Repayment of Change in Value of Principal and Investor's Rate Stock Price Shares Interest* of Return 30% increase $26,000 $10,900 51% No change 20,000 10,900 30% decrease 14,000 10,900 -69 -9