Answer:
Go through each equation and find the amount of elements in each part of the equation, they should have the same amount on both sides.
For 1.
Reactants:
C - 1
H - 4
O - 2
Products:
C - 1
H - 4
O - 4
The difference in the amount of atoms for Hydrogren and Oxygen in the reactants and products make this equation a skeleton equation aka an unbalance equation.
