X-number
8x-20=15+x (subtract x)
7x-20=15 (then add 20)
7x=35 (then divide by 7)
I think you've got it from now, if not, just do 35 divided by 7. But go over the steps, so that you know how to do these types of questions.
The formula for area in terms of radius is
... A = πr²
Solving this for r, we get
... A/π = r²
... r = √(A/π) . . . . . formula for the radius
For your given area, the radius is approximately
... r = √(401.92/3.14) = √128 = 8√2
... r ≈ 11.3 . . . yards
If the equation is f(x)=2x+5
The domain is 2x+5
If the range is 1, the domain is 7
Hopefully this makes sense!