Let us solve the questions one by one:

Q7: Identify the number to be written in the empty place.

We are given a grid:

8  3  4
1  5  ?
6  7  2

This grid likely represents a magic square where the sum of the numbers in every row, column, and diagonal should be the same.

1. The first row sums up to: $8 + 3 + 4 = 15$.
2. The second row is: $1 + 5 + ? = 15$.
   Solving for the missing number: $? = 15 - (1 + 5) = 15 - 6 = 9$.

The missing number is 9.

Q8: Complete the following puzzle.

The puzzle involves symbols and equations:

🔷 + ⬜ = 8
⬜ + 🔶 = 6
🔷 + 🔶 = 13

We need to solve for 🔷, ⬜, and 🔶. This can be done systematically:

1. From equation 1: $🔷 + ⬜ = 8$ → $⬜ = 8 - 🔷$.
2. Substitute $⬜ = 8 - 🔷$ into equation 2:
   $(8 - 🔷) + 🔶 = 6$ → $🔶 = 6 - 8 + 🔷$ → $🔶 = 🔷 - 2$.
3. Substitute $🔷 + 🔶 = 13$ (equation 3):
   $🔷 + (🔷 - 2) = 13$ → $2🔷 - 2 = 13$ → $2🔷 = 15$ → $🔷 = 7.5$.
4. Now substitute $🔷 = 7.5$ back:
   $⬜ = 8 - 7.5 = 0.5$, and $🔶 = 🔷 - 2 = 7.5 - 2 = 5.5$.

The values are:

• $🔷 = 7.5$
• $⬜ = 0.5$
• $🔶 = 5.5$.

Q9: What can be added in place of the question mark?

The cross-shaped arrangement is as follows:

      30
       |
  12 - 36 - ?
       |
      14
       |
       49

Observing the structure, this puzzle likely involves some mathematical relationship (e.g., addition, multiplication, etc.) between the numbers surrounding the central box. Let us check for patterns:

1. Look at vertical relationships: $30 → 36 → 14 → 49$:
   $30 + 14 = 44$, which is close to 49. This might indicate summing or averaging.

2. Horizontal relationships: $12 → 36 → ? → 35$:
   We suspect the missing number $?$ relates to the center $36$.
   Trying subtraction:
   $36 - 12 = 24$, $35 - 36 = -1$. This approach does not fit.

3. Let’s look for squares or other patterns.
   The numbers $36, 49, 12, 30$ seem connected to squares:
   $36 = 6^2, 49 = 7^2, 30 \approx 5.5^2, 12 = 3.5^2$.
   So, the missing number must complete this progression. $? = 35 = 5^2 - 1$.

Thus, $? = 35$.