21=-20-8(2х-0,5)

To solve the equation 21 = -20 - 8(2x - 0.5), we can follow these steps:

1. Distribute the -8 to the terms inside the parentheses:
21 = -20 - 8 * 2x + 8 * 0.5

2. Simplify the equation by performing the multiplication:
21 = -20 - 16x + 4

3. Combine like terms:
21 = -16x - 16

4. Move the constant term to the other side of the equation by adding 16 to both sides:
21 + 16 = -16x - 16 + 16
37 = -16x

5. Divide both sides by -16 to solve for x:
x = 37 / -16

6. Simplify the fraction if possible:
x ≈ -2.3125

Therefore, the solution to the equation 21 = -20 - 8(2x - 0.5) is approximately x ≈ -2.3125.