# Question #81dd7

##### 1 Answer

The **first** must be reversed (cool rhyme!)

#### Explanation:

When you "add together" two or more chemical equations, it goes similarly as algebra: equal quantities on opposite sides of either reaction can cancel out.

Here's what I mean by this:

Our two equations are

Here, there must be two duplicate quantities is a given color to cancel out. As you may see, neither red nor blue contains a duplicate species. However, if we reversed the first equation, we would then have

Two quantities can cancel out, leaving behind the blue equation: