Answer:
Add 6 each time.
Step-by-step explanation:
Figure 1 has 4 tiles.
To go from figure 1 (4 tiles) to figure 2 (10 tiles), you added 6 tiles.
To go from figure 2 (10 tiles) to figure 3 (16 tiles), you added 6 tiles.
∴ the rule is to add 6 tiles each time.
