X=8 y=20 find y when x=42

In this problem, we need to use the concept of proportions. Proportion says that two ratios (or fractions) are equal. So, we have two numbers, namely:

So, the given proportion is:

That is, x-out-of-y is equal to 2-out-of-5

On the other hand, we know that , so by using the previous proportion we have:

Answer

y= 105

Explanation

X=8

Y=20

So,

x/y = 8/20

      = 2/5

x=(2/5)y

y= (5/2)x

When x=42

y=(5/2)×42

   =105

let's call the solutions x₁ = (5 - 2√7)/3 and x₂ = (5 + 2√7)/3

then the equation is (x-x₁)(x-x₂) = 0

if you fill that in you get a lot of numbers which you can recognize as ax²+bx+c=0.

step-by-step explanation:

you can see that a=1 (there is just an x²)

b = (-5 -2√7 + 2√7 - 5)/3 = -10/3

c = -2√7)/3 ) * (-5+2√7)/3) = -1/3

so your answer is 3x^2 – 10x – 1 = 0