Prior Knowledge Questions (Do these BEFORE using the Gizmo.) Suppose you want to buy a new t-shirt for $15. So far, you have saved $9 from your allowance. 1. Write an equation to model the situation. Let x be the amount you need. 2. How much more money do you need? Explain. 1. Activity: Get the Gizmo ready: Solving an equation e You should see the equation x + 3 = 7 at the top left corner. If not, click Refresh in your browser. Notice that the Gizmo has already modeled the equation x + 3 = 7 with tiles for you. A. How many tiles are used to model \"x + 3"? x-tiles: 1-tiles: . How many tiles are used to model \"7"? x-tiles: 1-tiles: . In order to solve the equation, you must isolate the variable, or get x by itself. In this case, you need to remove three 1-tiles to isolate the x. Drag the three 1-tiles out of the left-hand bin. (You can either remove them one at a time, or you can drag a box around all three and remove them together.) . When you remove a tile from the left side, a tile is also remaoved from the right side. Why do you think this is? When the x-tile is by itself, how many 1-tiles remain on the right? What is the solution to the equation x + 3 =77 F. G. What is the solution to the equation x + 3 =77 Substitute the solution into the given equation. What do you get? 2. Click New. The next equation you should see is x 4 = 5. A To solve the equation, you need to isolate x. Why can you not remove four 1-tiles from both sides? . Add four 1-tiles to both sides of the equation. You now have four zero pairs on the left side. Drag a box around them and remove them. . Why do you think you can remove these tiles from the left side without removing any from the right side? . What is the solution to the equation x 4 = 5? 3. Click New and work through more problems in the Gizmo. 4. %, Solve each equation below, by hand or click the box to select EDIT to use the drawing tool. Just as with tiles, be sure to isolate the x, and whatever you do to one side of the equation, be sure to do it to the other side also. A x+5=12 D. x-4=-2 B. x+6=2 E. x-7=10