- FIND x when “8 times the sum of the number and 5 is equal to 20 more
than 4 times the number."

Step-by-step explanation:

8(x+5)=20+4x

8x+8*5=20+4x

8x-4x=20-40

4x=-20

x=-5

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