C3H8 + 5O2 → 3CO2 + 4H2O

Here's how to balance it:

1. Count atoms on each side:

* Reactants: 3 C, 8 H, 2 O

* Products: 1 C, 2 H, 3 O

2. Balance Carbon:

* Put a 3 in front of CO2: C3H8 + 5O2 → 3CO2 + 4H2O

3. Balance Hydrogen:

* Put a 4 in front of H2O: C3H8 + 5O2 → 3CO2 + 4H2O

4. Balance Oxygen:

* There are now 10 oxygen atoms on the product side.

* Put a 5 in front of O2: C3H8 + 5O2 → 3CO2 + 4H2O

Now the equation is balanced with 3 carbon, 8 hydrogen, and 10 oxygen atoms on both sides.