The purpose of this activity is for students to match expressions with three addends to the expression with the same value. This activity sets the groundwork for the next activity in which students make sense of addition equations with expressions on both sides of the equal sign. 

MLR2 Collect and Display. Circulate, listen for, and collect the language students use as they work with partners. On a visible display, record words and phrases such as: “equivalente”, “expresión”, “el mismo”, “diferente” y “suma” // “equivalent,” “expression,” “the same,” “different,” and “sum.” Invite students to borrow language from the display as needed, and update it throughout the lesson.
Advances: Conversing, Speaking

• “¿Cómo supieron cuáles expresiones tienen el mismo valor?” // “How did you know which expressions have the same value?” (I looked for ways to make 10 and the amount left to add.)
• “¿Qué patrones observaron?” // “What patterns did you notice?” (They are all teen numbers. They are all 10 + facts.)

The purpose of this activity is for students to determine whether equations with an expression on each side of the equal sign are true. Each equation has an expression with three addends on one side and a expression on the other. Students do not need to find the value of each expression in order to determine if the equation is true, but some students may do so. In this activity, students have an opportunity to look for and make use of structure (MP7) because they apply the associative property and pattern to determine whether equations are true.

• Invite previously identified students to share.
• “¿Este razonamiento demuestra que la ecuación es verdadera? ¿Por qué sí o por qué no?” // “Does their reasoning prove whether the equation is true? Why or why not?” (Yes, we can see that it is on the 10-frame. Yes, we see that is 10, and then there are 8 left. That is the same as .)

The purpose of this activity is for students to write a  expression that is equivalent to a given expression. Each expression given has three addends, two of which make a ten.

• Display each expression.
• “Para que sea más fácil sumar tres números, podemos reescribir cada expresión como una expresión del tipo ‘10 más otro número’” // “In order to make adding three numbers easier, we can rewrite each expression as a 10 plus another number expression.”
• Invite students to say the value of each  expression together.