F (x) = 4 (2) - 20 f (10)
Multiply 4 by 2
And multiply 10 by -20
F (x) = 8 - 200 f
You will add 200f to both side of the equation
F (x) + 200f = 8
Now subtract f (x) from both sides of the equation
200f = 8 - f (x)
Now divide each term in 200f = 8 - f (x) by 200 and simplify
F= 1/25 - f(x)/200