What is 90 percent of 20

Ametalworker has a metal alloy that is 30? % copper and another alloy that is 55? % copper. how many kilograms of each alloy should the metalworker combine to create 90 kg of a 50? % copper? alloy?

Aline has a slope of 1/4 and passes through point (0.4,-1/2). what is the value of the y-intercept?

Solve for n? [tex]z = \frac{3}{4} mn[/tex]