If the solubility of o2 at 0.370 atm and 25 °c is 15.3 g/100 g h2o, what is the solubility of o2 at a pressure of 2.40 atm and 25 °c?

According to Henry's law:

C = K P         when,
C is the solubility of a gas at a constant temperature in a particular solvent.
K is the Henry law constant 
p is the pressure of the gas

we have the pressure and the solubility so we will get the K at first:
by substitution:
0.153 = K * 0.37atm 
K= 0.4
∴ C when P = 2.4 atm
∴ C = 0.37 * 2.4 atm = 0.888   = 88.8 g/100g H2O

You use the atomic number to find out how many protons and neutrons there are in the atom. you use the atomic mass to find out how many protons and electrons there are in the atom. 

Its a hope this