how to integrate , please help, I have no idea what to do, I would appreciate if you show your work with steps.

3x + 4y = 5 x- 3y = -7 solve by substitution

How many quarts of a 50% solution of acid must be added to 20 quarts of a 20% solution of acid in order to get a 40% solution of acid?

Here are the 30 best lifetime baseball batting averages of all time, arranged in order from lowest to highest: 0.319, 0.329, 0.330, 0.331, 0.331, 0.333, 0.333, 0.333, 0.334, 0.334, 0.334, 0.336, 0.337, 0.338, 0.338, 0.338, 0.340, 0.340, 0.341, 0.341, 0.342, 0.342, 0.342, 0.344, 0.344, 0.345, 0.346, 0.349, 0.358, 0.366 if you were to build a histogram of these data, which of the following would be the best choice of classes?