How many protons are in an isotope of oxygen-15?

Can someone me with 3 and 4 plz. this is for masteries test.

An animal cell loses the ability to convert energy stored in food to energy that the cell can use. which of the cell's organelles has stopped working? a.the mitochondria b.the nucleus c.the vacuoles d.the endoplasmic reticulum

Correct relationship between molecular formula and empirical formula