Help chemistry week test

Large helium-filled balloons are used to lift scientific equipment to high altitudes. what is the pressure inside such a balloon if it starts out at sea level with a temperature of 10.0ºc and rises to an altitude where its volume is twenty times the original volume and its temperature is – 50.0ºc ?

Elements in group 2 are all called alkaline earth metals. what is most similar about the alkaline earth metals?

Ariver current has a velocity of 5km/h relative to the shore, and a boat moves in the same direction as the current at 5 km/h relative to the river. how can the velocity of the boat relative to the shore be calculated?