What is the result when atoms combine in fixed ratios?

If the atomic mass of an atom is 34 and the atom contains 13 protons, how many neutrons does the atom contain?

What must happen before a body cell can begin mitotic cell division

Agas is contained in a thick walled balloon when the pressure changes from 1.21 atm to 2.52 the volume changes from 3.75 l to 1.72 l and the temperature change from 293k to blank k