Hello, Jada,
First balance the equation.
2H2 + 1O2 = 2H2O
Then find the molar masses and calculate the number of moles of both H2 and H2O with the given masses.

2 
H2 
1 
O2 
= 
2 
H2O 
g/mole 

2 

32 


18 
Grams = 

33.7 

267.556 


301 
moles = 

16.85 

8.36111 


16.72 
Moles = grams/molar mass
· Water at 301 grams is 16.7 moles of water.
· Hydrogen at 33.7g is 16.9 moles of H2.
Theoretically, those two numbers should be equal since the molar ratio between H2 and H20 in the equation is equal to one (2/2). The H2O number is less than the 16.85 moles of H2, indicating some of the hydrogen did not react. Therefore, we will use the moles of water to determine O2 consumption.
The ratio of O2 to H2O in the balanced equation is ½. Therefore, ½ mole of O2 is consumed for every mole of H2O produced. That leads to 8.36 moles of O2 consumed to produce the 16.7 moles of H2O.
Convert 8.36 moles of O2 to grams O2 by multiplying by the molar mass of O2: 8.36moles*32g/mole = 268 grams.
I hope this is clear,
Bob