A chemist needs 40 liters of a solution that is 20% acid for a certain experiment, but she has only a solution that is 15% acid and a solution that is 40% acid. How many liters of the 15% and
the 40% solutions should she mix to get what she needs?

Two vertices of a polygon are (7, −18) and (7, 18) . what is the length of this side of the polygon? enter your answer in the box. units

Find the number of real number solutions for the equation. x2 + 5x + 7 = 0 0 cannot be determined 1 2

Martha has a deck of cards. she has lost some of the cards, and now the deck only contains nine spades, eleven diamonds, eight clubs, and twelve hearts. martha predicts that whenever she draws a card from the deck without looking, she will draw a club one-fifth of the time. which activity would best allow martha to test her prediction? a. randomly draw a card from the box and see if it is a club. b. randomly draw a card. then, continue to draw another card until all eight clubs are drawn. c. randomly draw and replace a card 120 times. then, observe how close to 30 times a club is drawn. d. randomly draw and replace a card 100 times. then, observe how close to 20 times a club is drawn.