-300=-20(-3b)

Solution for -300=-20(-3b) equation:

Simplifying
-300 = -20(-3b)

Remove parenthesis around (-3b)
-300 = -20 * -3b

Multiply -20 * -3
-300 = 60b

Solving
-300 = 60b

Solving for variable 'b'.

Move all terms containing b to the left, all other terms to the right.

Add '-60b' to each side of the equation.
-300 + -60b = 60b + -60b

Combine like terms: 60b + -60b = 0
-300 + -60b = 0

Add '300' to each side of the equation.
-300 + 300 + -60b = 0 + 300

Combine like terms: -300 + 300 = 0
0 + -60b = 0 + 300
-60b = 0 + 300

Combine like terms: 0 + 300 = 300
-60b = 300

Divide each side by '-60'.
b = -5

Simplifying
b = -5