Answer
The absolute pressure of the gas is $114.0~cm~Hg$
Work Step by Step
Since the mercury stands 40.0 cm higher in the tube that is open to the air, the gauge pressure of the gas is 40.0 cm Hg.
Since the barometer reads 74.0 cm Hg, the atmospheric pressure is 74.0 cm Hg.
We can find the absolute pressure of the gas:
$P_{abs} = P_{atm} + P_g$
$P_{abs} = (74.0~cm~Hg)+(40.0~cm~Hg)$
$P_{abs} = 114.0~cm~Hg$
The absolute pressure of the gas is $114.0~cm~Hg$.
