So 13 divided by 3 is 4 but where is the 4 coming from because 4 groups of 3 is 12 so 13 minus 12 is 1 so how dose the 4 make it the remander

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

Ur environment is very sensitive to the amount of ozone in the upper atmosphere. the level of ozone normally found is 4.04.0 parts/million (ppm). a researcher believes that the current ozone level is not at a normal level. the mean of 2525 samples is 4.44.4 ppm with a standard deviation of 0.80.8. assume the population is normally distributed. a level of significance of 0.020.02 will be used. make the decision to reject or fail to reject the null hypothesis. answer tables

Can someone me with my math problem pls my teacher is on my back about this