This is 2nd time blogging about this problem. 1st time-around post is here.

**Scenario**:

What do you notice (facts)? |
What do you wonder (questions)? |

different prices | why are they buying these |

Adding 3 extra coffees cost more by a little | How much with it cost for 4 coffees and 4 muffins ? |

why is the kid buying coffee? | whys the kid buying coffee? |

The totals are different on each side.
One side has less drinks. |
How much is each item? |

nothing | |

2 different cost | How much the cupcake cost each one How much the coffee cost each one |

there’s money, drinks, cupcakes | how much each coffee and cupcake is |

For the first indivdual, it costs $8.85 for three cupcakes and three coffee cups.
For the second person, it costs $5.35 for three cupcakes and one cup of coffee. |
Im curious about what brand of coffee that they are buying. It seems potentially no name or even something like a corner store kinda coffee. ew.
oh yeah also how much do they each cost? |

The total cost are different | How much it cost in each item |

I notice cupcakes , coffee , a boy and a girl | how much is each |

The person on the left has more coffee and is going to spend more | What is the individual price of the coffee and the muffins |

– They both ordered 3 muffins, but one had 3 cups of a drink and the other ordered one. – The one that ordered 3 cups, have to pay more. |
– How much does one drink cost? – How much does one muffin cost? – Does the person on the right have a better deal than the person on the left? |

Different prices and different subjects | How much does it cost for each item |

Adding 3 more cups of of coffee is a little bit more than getting one cup of coffee | how much is one cup of coffee |

Different objects in both pictures | Why did the person on the left buy more |

diffent | how much money does it cost to for one cup of coffee and one muffin |

**Solve** for the cost of 1 muffin as well for the cost of 1 coffee (red/orange annotations are mine during whole class discussion):

They all solved it by subtracting what was common to both orders & splitting the remaining cost amongst the remaining coffees. The follow up questions on Pear Deck asked them to create an equation for each order. I then did some direct teaching on the side showing them how to do elimination using 2 different equations. Then I asked them to go to their board and use elimination to solve this problem. They started this on day 1 above but we class ended & we hadn’t finished. So on day 2, with a new group of partners & fresh boards, I sent them up to use elimination to solve fully:

We compared the solutions of the different groups and picked out the one board that had the most correct formatting of an algebraic solution. I drew parallels between their work during elimination and their earlier logic, pointing out how they are both eliminating something (I explained this more in depth & more eloquently).

We then did a quick check with Desmos:

The individual practice to wrap up was a Khan Academy exercise set on elimination not involving any multiplication of equations.

Activity available here.

– Laura Wheeler (Teacher @ Ridgemont High School, OCDSB; Ottawa, ON)

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