Find measure of DF. Explanation would be great!

(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 ?

If 10 men take 18 days to mow 60 acres of grass, how long will 15 men take to mow 80 acres?

Solve this equation using substitution. {4x + y = −2} {4x + 6y = 44}