The purpose of this activity is for students to solve a Take From, Result Unknown story problem in which the minuend is a teen number. Students represent and solve the problem in any way that makes sense to them.

Monitor for and select students with the following approaches to share in the synthesis:

• Cross off or remove 8 objects from the incomplete 10-frame (last 2 rows of bin) and count the remaining objects.
• Cross off or remove 8 objects from the incomplete 10-frame and recognize the remaining objects as 10 and 1.
• Know the ten stays the same, and subtract .

The approaches are sequenced from more concrete to more abstract to help students understand different approaches to finding the solution that do not require decomposing a ten. This sequence also helps students begin to notice ways to think about subtracting ones from ones. Aim to elicit both key mathematical ideas and a variety of student voices, especially students who haven’t shared recently.

• Invite previously selected students to share in the given order. Record or display their work for all to see.
• Connect students’ approaches by asking:
  • “¿En qué se parecen las formas en que ellos resolvieron el problema? ¿En qué son diferentes?“ // “What is the same about how they solved the problem? What is different?” (They are the same because they all take away 8 from 19. They all got 11. They all took the 8 away from the 9. They are different because one counted to find the answer and the others didn’t.)
• Connect students’ approaches to the learning goal by asking: 
  • “¿Qué observan sobre la forma en que están organizadas las fichas?“ // “What do you notice about how the game pieces are organized?” (They are in two 10-frames. There is a full 10 and 9 more.)
  • “¿Cómo les ayudó esto a resolver el problema-historia?“ // “How did that help you solve the story problem?” (I took away from the 10-frame with only 9 game pieces so that I could keep the full 10-frame.)
  • “¿Dónde ven un 10 completo en lo que hizo cada estudiante?” // “Where do you see a full ten in each students' work?” (In the drawing, they didn’t cross out any pieces from the full 10-frame —the top 2 rows of the bin. In the other way, they knew 19 is 10 + 9 and they only subtracted from the 9, so there is still a full 10.)

• Display each equation with the unknown value.
• Invite students to share how they found each unknown value.

The purpose of this activity is for students to learn Stage 5 of the Shake and Spill center. Students use between 11‒20 counters. One partner shakes, spills, and covers up the yellow counters with a cup. The other partner determines how many counters are under the cup and explains how they know. Both partners record the round with an equation.

The recording sheet asks for an expression or an equation. During this stage, students should complete an equation.

MLR8 Discussion Supports. Synthesis: Provide students with the opportunity to rehearse what they will say with a partner before they share with the whole class.

• Display five red counters and cover ten yellow counters under the cup.
• “Mi compañero y yo estamos jugando con 15 fichas. ¿Cuántas fichas amarillas están debajo del vaso? ¿Cómo lo saben?” // “My partner and I are playing with 15 counters. How many yellow counters are under the cup? How do you know?”