Answer:
x=9
Step-by-step explanation:
The ratio House blend/Organic Free Trade blend is the same and must remain the same.
So, the proportion is:

Where x is the unknown amount of the Organic Free Trade blend.
So, from the proportion, we have:

Answer: 156 pounds of Organic Free Trade blend
Yes, that is the famous first Pythagorean triplet: 3²+4²=5²
or
For three lengths to be able to form a triangle, it suffices that every one of those lengths is shorter than the sum and longer than the difference of the other two.
It is enough to check just one side.
So,
3 + 4 > 5
4 - 3 < 5
Your triangle is constructible.