What equation could be used to find how many grams of mass is in 15.6 kilograms

Reflect the point (7,0) across the y-axis

Acompany that manufactures and sells guitars made changes in their product range. from the start they had 20 models. then they reduced the number of models to 15. as a result, the company enjoyed a 10% increase in turnover. - how much did the stock level change? in (%)

Solve for x and y: 217x + 131y = 913; 131x + 217y = 827