1 heart and I’ll answer this

**Answer:**

4

**Step-by-step explanation:**

He should add 4 black blocks because there are a total of 4 other blocks, and in order to have a probability of 50%, the number of black blocks needs to be equal to the total number of the other colored blocks.

**Answer:**

4

**Step-by-step explanation:**

3^2=9

-2 times 3 = -6

9-6+1=4