-3(b+7)=4(b-2b)

Solution for -3(b+7)=4(b-2b) equation:

Simplifying
-3(b + 7) = 4(b + -2b)

Reorder the terms:
-3(7 + b) = 4(b + -2b)
(7 * -3 + b * -3) = 4(b + -2b)
(-21 + -3b) = 4(b + -2b)

Combine like terms: b + -2b = -1b
-21 + -3b = 4(-1b)

Remove parenthesis around (-1b)
-21 + -3b = 4 * -1b

Multiply 4 * -1
-21 + -3b = -4b

Solving
-21 + -3b = -4b

Solving for variable 'b'.

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

Add '4b' to each side of the equation.
-21 + -3b + 4b = -4b + 4b

Combine like terms: -3b + 4b = 1b
-21 + 1b = -4b + 4b

Combine like terms: -4b + 4b = 0
-21 + 1b = 0

Add '21' to each side of the equation.
-21 + 21 + 1b = 0 + 21

Combine like terms: -21 + 21 = 0
0 + 1b = 0 + 21
1b = 0 + 21

Combine like terms: 0 + 21 = 21
1b = 21

Divide each side by '1'.
b = 21

Simplifying
b = 21