Please help! this is worth 10% of my grade in math :)

Solve the following pair of equations for x and y: ax/b_ by /a= a +b; ax - by = 2ab

Write the equation of the line that passes through (3, 4) and (2, −1) in slope-intercept form. (2 points) y = 3x − 7 y = 3x − 5 y = 5x − 11 y = 5x − 9

There are a total sales of 2,000 dollars on monday on tuesday sales dropped 10% on wednesday sales dropped another 20% compared with tuesday from wednesday to thursday sales increases by an equal amount to 25% of monday total sales what is the net change in dollars on total sales from monday to tuesday