If you’re withdrawing money from an account, you are taking away money. So, you’ll have to use subtraction.
If you’re depositing money to an account, you are adding more money. So, you’ll use addition.
What are you trying to find out: At what week will both Minnie And Mickey Mouse have an equal account balance? How much money will they both have in their account at that week?
So we can find the answer by using the equation, 250 - 15x = 100 + 10x where the variable x represents the amount of weeks.
Workspace:
You can either replace the x with multiple numbers until you get your answer or solve the problem a quicker way.
1. Move all terms containing x to the left
250 - 15x = 100 + 10x
Use inverse operations, so instead of + 10 you’ll - 10. You can only add, subtract, multiply, and divide alike terms.
250 - 15x - 10x = 100
250 - 25x = 100
2. Move all terms that do NOT contain x to the right
To do this you must do inverse operations, so - 250, remember that you can only preform operations on alike terms.
-25x = 100 - 250
-25x = - 150
3. Divide each term by -25
A variable next to a number means multiplication, and division is the opposite of multiplication.
-25x/-25 = -150/-25
Cancel out both -25s on the left but leave the x
x = -150/-25
x = 6
So, at week 6 both will have the same amount of money in their account. We still have to answer the second question, what will the amount be? But, all we have left to do is replace the x with 6, and figure out the rest, which should be easy.
250 - 15(6) = 100 + 10(6)
250 - 90 = 100 + 60
160 = 160
Solution: At week 6, both Mickey and Minnie Mouse will have an equal amount of money in their account, which would be $160.