8x^2 - 3(x - 4) = 0
Expanding the equation, we get:
8x^2 - 3x + 12 = 0
Now, solve this quadratic equation using the quadratic formula or factorization method.

5x^3 - x(2x - 3) = 3x
Expand the equation:
5x^3 - 2x^2 + 3x = 3x
Rearrange terms:
5x^3 - 2x^2 = 0
Factor out x^2:
x^2(5x - 2) = 0
Solve for x, either x = 0 or 5x - 2 = 0

4x - 0.2x(x - 20) = x^3
Expand the equation:
4x - 0.2x^2 + 4x = x^3
Rearrange terms:
-0.2x^2 + 8x - x^3 = 0
Solve this equation for x.

9x(x - 3)(x - 4)(x - 5) = 20
Expand the equation on the left side:
9x(x^3 - 12x^2 + 47x - 60) = 20
Now, solve the resulting equation for x.