Substitution.
Here is an example.
Let x be equal to 3 and y equal to 3.

From this we can conclude that the values of both x and y are equal to three therefore x and y have the same value and are equal.

Here in your case we have:

Hope this helps.
r3t40
Answer:

Step-by-step explanation:
♡ Good Lessons ♡
Answer:
a + m = 2+ a
Step-by-step explanation:
We don't know the amount of apple granola and the amount of the maple granola. So we just set an equation.