Answer:
The method of collecting data that involves response variables is the (Experimental) method, and the method in which conclusions are drawn by comparing the data collected from two groups without regulating is the (Observational) method.
Answer: 3.6cm
Step-by-step explanation:

Using the volume formula; solve for a;
![a^2=\frac{V}{h}\\ a=\sqrt[]{\frac{V}{h} }](https://tex.z-dn.net/?f=a%5E2%3D%5Cfrac%7BV%7D%7Bh%7D%5C%5C%20a%3D%5Csqrt%5B%5D%7B%5Cfrac%7BV%7D%7Bh%7D%20%7D)
![a=\sqrt[]{\frac{104cm^3}{8cm} }](https://tex.z-dn.net/?f=a%3D%5Csqrt%5B%5D%7B%5Cfrac%7B104cm%5E3%7D%7B8cm%7D%20%7D)
![a=\sqrt[]{13cm^2}](https://tex.z-dn.net/?f=a%3D%5Csqrt%5B%5D%7B13cm%5E2%7D)

Hello :
<span> -3 = -15 + a
add : 15
-3 +15 = -15 +15 +a
12 = a
a = 12</span>