Introduction:

I am absolutely at the end of the equations with one unknown, but there is one more thing that I need to exercise. 

That is, again, the equation with one unknown, but how to use it in math problems

The math problem:

I will work on this exercise:

There are 5 times as many coins in the first 
piggy bank as in the second one. 
If 20 coins are taken out of the first piggy bank 
and 12 coins are added to the second piggy bank, 
the two piggy banks will have the same number of coins.

How many coins are in the second piggy bank?

I start working by reading the condition really carefully. 

Then I need to tell the information that we don't know with an unknown.

If we follow this, I can tell that the coins in the second piggy bank are x, so the coins in the first will be 5x, because I know that from the condition.

Now, if I look at the other part of the condition and use it, the equation will become like this:

In the first piggy bank: 

5x

In the second piggy bank: 

x

I take out 20 from the first piggy bank:

5x - 20

I add 12 to the second piggy bank:

x + 12

And then the coins in the two piggy banks are the same:

5x - 20 = x + 12

The solution of the equation:

I see that the solution now is really easy when I know how to make it.
I solve the equation:

5x - 20 = x + 12

I put the unknowns at one side by transferring numbers with the opposite sign and it becomes like this:

5x - x = 12 + 20

After this we solve the equation:

5x - x = 12 + 20
4x = 32
X = 32 : 4
X = 8

The answer of the exercises:

Back to the exercises, but now I know x. I see what it was x and when I know how much is it I can easily tell this:
 

In the first piggy bank: 5 x 8 = 40

In the second piggy bank: 8

If we look to the question in the exercise which is how many coins are in the second piggy bag, we can easily tell the answer.

=> Answer: 8 coins

End:

Now I know everything about the equations with one unknown, so you can also learn something from me. Now be happy that I finish this notes. See you next time! Bye!