The product of x and y, written in three different ways

(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 ?

Can someone me do math because i am having a breakdown rn because i don’t get it

Acircle has a circumference of 7.850 units. what is its radius?