Please help I don't know how to do this I am confused

What number should be added to the expression x^2+3x+ in order to create a perfect square trinomial? 3/2 3 9/4 9

Round each of the decimals to the nearest hundredth a. 0.596 b. 4.245 c. 53.6843 d. 17.999

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?