Find the area and perimeter

How much dextrose 70% must be mixed with dextrose 5% to prepare 1,000 ml of dextrose 20%?

What is the axis of symmetry of the function f(x)=-(x+ 9)(x-21)

Cherie works in retail and her weekly salary includes commission for the amount she sells. the equation s=400+0.15c models the relation between her weekly salary, s, in dollars and the amount of her sales, c, in dollars. interpret the slope of the equation.