A scientist needs 80 liters of a 30% solution of alcohol. She has a 20% solution and a 60% solution available. How many liters of the 20% solution and how many liters of the 60% solution should she mix to make the 30% solution?

If f(x)=-x^2+6x-1 and g(x)=3x^2-4x-1,find(f+g)(x)

Set $r$ is a set of rectangles such that (1) only the grid points shown here are used as vertices, (2) all sides are vertical or horizontal and (3) no two rectangles in the set are congruent. if $r$ contains the maximum possible number of rectangles given these conditions, what fraction of the rectangles in set $r$ are squares? express your answer as a common fraction.

Tatiana reads 40 pages of her book every night for x number of nights. write an expression that shows the number of pages she has read