How do you change 37/40 into a decimal

The ph level of a blueberry is 3.1 what is the hydrogen-ion concentration [h+] for the blueberry

If 7x=9y, y/z = 7/5 , then x/z = (a) 2/7 (b) 7/9 (c) 9/5 (d) 9/7 (e) 5/9

The center on a target has a diameter of 5 inches. the whole target has a diameter of 25 inches. complete the explanation for what part of the whole target is the center. the center of the target takes up % of the whole target.