Question

C8H18+ O2> CO2+ H2O how to make this balanced?

Answer 1

product:
C: 1
O:3
H: 2

reactant:
C: 8
H: 18
O: 2

first you need to put probably an eight in front of the Carbon.
Next, add a coefficient of 9 to Hydrogen
finally, add a 3 INSTEAD of a 2 to Oxygen

should look like:
C8H18+O3>C8O2+H9O