Abubble of helium gas has a volume of 0.650 ml near the bottom of a large aquarium where the pressure is 1.54 atm and the temperature is 12°c. determine the bubble's volume upon rising near the top where the pressure is 1.01 atm and 16°c. assume that the number of moles of helium remains constant and that the helium is an ideal gas.

For this question we can use the combined gas law equation.
for a fixed amount of gas
where P - pressure , V - volume , T- temperature and k - constant 

Where parameters for the first instance are on the left side and parameters for the second instance are on the right side of the equation 
temperature in K 
T1 = 12 °C + 273 = 285 K
T2 - 16 °C + 273 = 289 K
substituting the values in the equation 

V = 1.00 mL