determine the mass of carbon4oxide produced from burning 104g of ethyne

But our (C=12,O=16,H=1)

The equation is balanced but your answer is wrong.

2C2H2+5O2==>2H2O +4CO2

2moles. 4moles
R.M.M C2H2=26g
R.M.M CO2=44g
26g of C2H2 ==> 44g of CO2
xg of C2H2 ==>104g of CO2
: xg = 104 × 26 = 2,704 = 61.5
44 44
My answer is 61.5

61.5g/mol

Ur answers are wrong the answer supposed to be 356g

How (why) did you get O2 into your calculations. The problem asks for grams CO2.

mols C2H2 = 104/26 = 4.0
Convert mols C2H2 to mols CO2. That's 4.0 mols C2H2 x (4 mols CO2/2 mols C2H2) = 8 mols CO2.
Now convert mols CO2 to grams. That's grams = mols CO2 x molar mass CO2 = 8*44 = ?
BTW, your answer for grams O2 isn't right. your 52/7 = 160/x should be 52/104 = 160/x and for oxygen x = 320. I don't see 7 in the problem anywhere.

2C2H2 + 5O2 ==> 2H2O + 4CO2

RMM of C2H2=26g therefore 1mol of C2H2 = 26g
Since 2mol of C2H2 required 5mol of oxygen 2mole of C2H2 = 2 ×26=56g & 5mol of O2= 5×32=160g
Hence 52g of C2H2 ==>160g of O2
7g of C2H2 ==>Xg of O2
Cross multiply
X=160×78÷52
X=240g