Why use trial and error ?
Why not just solve the quadratic equation ?
The picture says x² + 3 = 5x
Subtract 5x from each side: x² - 5x + 3 = 0
Use the quadratic formula to solve this equation.
From the looks of this problem, I have a hunch that
you may be studying the quadratic formula and how
to use it, in math right now, so I'm not going to write
the whole thing out.
I'll just point out that A=1, B= -5, and C=3 .
And x = (1/2) (5 plus or minus √13) .
x = roughly 4.303 and 0.697 . (both rounded)
If you have a craving for trial and error, then try some numbers
that are near those, and see how you come out.