Which of the following has all the justifications Kelsey used to solve this equation? (9th grade Algerbra 1)

Which values for a and b will create infinitely many solutions for this system of equations? ax-y=8 2x+y=b

(a) calculate the molarity of a solution that contains 0.0345 mol nh4cl in 400 ml of solution. (b) how many moles of hno3 are present in 35.0 ml of a 2.20 m solution of nitric acid? (c) how many milliliters of 1.50 m koh solution are needed to supply 0.125 mil of koh ?

Julia chooses a card at random from her set of cards. what is the probability that the card is labeled cat or hamster?