What is the constant proportion of y=2.9x

If given an equation of a line such as -1/2x+6 how would you create an equation of a line parallel and perpendicula to this line that goes through another point such as (4,10)

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 (%)

Will mark brainlist what is the slope of the line passing through the points (-2, -8) and (-3,-9)? -7/5-5/71-1