Collection of square root calculations displayed in a four-by-four grid.

The task involves solving square roots of various numbers. Let's go through each one step by step.

General Approach:

The square root of a number \( x \), denoted as \( \sqrt{x} \), is the value that, when multiplied by itself, gives \( x \). For example, \( \sqrt{4} = 2 \) because \( 2 \times 2 = 4 \).

We will solve each square root in the given image:

---

First Row:

1. \( \sqrt{0.12} \):
- This is not a perfect square, so we approximate:
\[
\sqrt{0.12} \approx 0.346
\]

2. \( \sqrt{0.04} \):
- This is a perfect square:
\[
\sqrt{0.04} = 0.2 \quad \text{(since } 0.2 \times 0.2 = 0.04\text{)}
\]

3. \( \sqrt{4.4} \):
- This is not a perfect square, so we approximate:
\[
\sqrt{4.4} \approx 2.1
\]

4. \( \sqrt{7.6} \):
- This is not a perfect square, so we approximate:
\[
\sqrt{7.6} \approx 2.76
\]

---

Second Row:

5. \( \sqrt{0.72} \):
- This is not a perfect square, so we approximate:
\[
\sqrt{0.72} \approx 0.849
\]

6. \( \sqrt{7.7} \):
- This is not a perfect square, so we approximate:
\[
\sqrt{7.7} \approx 2.78
\]

7. \( \sqrt{0.8} \):
- This is not a perfect square, so we approximate:
\[
\sqrt{0.8} \approx 0.894
\]

8. \( \sqrt{0.75} \):
- This is not a perfect square, so we approximate:
\[
\sqrt{0.75} \approx 0.866
\]

---

Third Row:

9. \( \sqrt{0.015} \):
- This is not a perfect square, so we approximate:
\[
\sqrt{0.015} \approx 0.122
\]

10. \( \sqrt{0.006} \):
- This is not a perfect square, so we approximate:
\[
\sqrt{0.006} \approx 0.077
\]

11. \( \sqrt{21} \):
- This is not a perfect square, so we approximate:
\[
\sqrt{21} \approx 4.58
\]

12. \( \sqrt{0.42} \):
- This is not a perfect square, so we approximate:
\[
\sqrt{0.42} \approx 0.648
\]

---

Fourth Row:

13. \( \sqrt{7.2} \):
- This is not a perfect square, so we approximate:
\[
\sqrt{7.2} \approx 2.68
\]

14. \( \sqrt{0.45} \):
- This is not a perfect square, so we approximate:
\[
\sqrt{0.45} \approx 0.671
\]

15. \( \sqrt{5.3} \):
- This is not a perfect square, so we approximate:
\[
\sqrt{5.3} \approx 2.30
\]

16. \( \sqrt{0.42} \):
- This is not a perfect square, so we approximate:
\[
\sqrt{0.42} \approx 0.648
\]

---

Fifth Row:

17. \( \sqrt{0.012} \):
- This is not a perfect square, so we approximate:
\[
\sqrt{0.012} \approx 0.11
\]

18. \( \sqrt{4.9} \):
- This is not a perfect square, so we approximate:
\[
\sqrt{4.9} \approx 2.21
\]

19. \( \sqrt{9} \):
- This is a perfect square:
\[
\sqrt{9} = 3 \quad \text{(since } 3 \times 3 = 9\text{)}
\]

20. \( \sqrt{0.084} \):
- This is not a perfect square, so we approximate:
\[
\sqrt{0.084} \approx 0.29
\]

---

Final Answers:

\[
\boxed{
\begin{array}{cccc}
\sqrt{0.12} & \sqrt{0.04} & \sqrt{4.4} & \sqrt{7.6} \\
\sqrt{0.72} & \sqrt{7.7} & \sqrt{0.8} & \sqrt{0.75} \\
\sqrt{0.015} & \sqrt{0.006} & \sqrt{21} & \sqrt{0.42} \\
\sqrt{7.2} & \sqrt{0.45} & \sqrt{5.3} & \sqrt{0.42} \\
\sqrt{0.012} & \sqrt{4.9} & \sqrt{9} & \sqrt{0.084}
\end{array}
}
\]

Approximate values:
\[
\boxed{
\begin{array}{cccc}
0.346 & 0.2 & 2.1 & 2.76 \\
0.849 & 2.78 & 0.894 & 0.866 \\
0.122 & 0.077 & 4.58 & 0.648 \\
2.68 & 0.671 & 2.30 & 0.648 \\
0.11 & 2.21 & 3 & 0.29
\end{array}
}
\]