Marshall determines that a gas has a gage pressure of 276 kpa what's the absolute pressure of this gas

To determine the absolute pressure of this gas, all you need to do is to add the value of atmospheric pressure and the value of gage pressure.

Atmospheric pressure is equivalent to 100 kPa. 
Gage pressure is 276 kPa.

Then, we add both values. 

N = 100 kPa + 276 kPa
N =  376 kPa

The absolute pressure of this gas is 376 kPa.

Hope this helps :)