A metal tank contains three gases: oxygen, helium and nitrogen. If the partial pressures of the three gases in the tank are 25 atm of oxygen, 12 atm of nitrogen and 15 atm of helium, what is the total pressure inside the tank

The independent variable is the type of music.the dependent variable is the pulse rate.the intervening variable is the age of the subject.if the mother does not like rock, her pulse is likely to not increase.the same might be true for the sister.the friend may like rap and gets excited.to establish cause/effect relationship, all of the subjects must be consistent.hope i .

The answer is 4 i don't know if its right let me see.