(In English), your question would state the following:
<span>Calculate the circumference and circumference of the circle entered in a square 8 cm long.
</span>
So when finding the answer this this question, we know that the circumference would be the complete area of a circle.
So, I believe we would want to find what is the radius and the diameter that would make this circumference 8

.
The radius would then be (1.274).
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Now in your own language (Croatian).
<span>Dakle, kad pronađemo odgovor na ovo pitanje, znamo da bi opseg bio cjelokupno područje kruga.
Dakle, vjerujem da bismo željeli otkriti što je radijus i promjer koji bi ovaj opseg mogao učiniti 8cm.
Radijus bi onda bio (1.274).</span>
Let red marbles be x.
Blue : 2x
Red : x
Yellow : x+8
2x + x + x + 8 = 56
4x = 48
x = 12
Red marbles: 12
Blue : 24
Yellow: 20
X*y=72
x = 5y-2
x=72/y
72/y=5y-2
72=5y^2-2y
5y^2 -2y - 72 = 0
(5y+18)(y-4)=0
y = -18/5 discard
or y = 4
4x=72
x=18
(18,4)
F(C) = 9/5C + 32
I'll just change F(C) to y and 9/5C to 9/5x.
y = 9/5x + 32
inverse...
x = 9/5y + 32
9/5y = x - 32
y = 5/9x - 160/9
Sooooo
F(C) = 5/9C - 160/9