91=0.5*7(B+12)

Solution for 91=0.5*7(B+12) equation:

Simplifying
91 = 0.5 * 7(B + 12)

Reorder the terms:
91 = 0.5 * 7(12 + B)

Multiply 0.5 * 7
91 = 3.5(12 + B)
91 = (12 * 3.5 + B * 3.5)
91 = (42 + 3.5B)

Solving
91 = 42 + 3.5B

Solving for variable 'B'.

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

Add '-3.5B' to each side of the equation.
91 + -3.5B = 42 + 3.5B + -3.5B

Combine like terms: 3.5B + -3.5B = 0.0
91 + -3.5B = 42 + 0.0
91 + -3.5B = 42

Add '-91' to each side of the equation.
91 + -91 + -3.5B = 42 + -91

Combine like terms: 91 + -91 = 0
0 + -3.5B = 42 + -91
-3.5B = 42 + -91

Combine like terms: 42 + -91 = -49
-3.5B = -49

Divide each side by '-3.5'.
B = 14

Simplifying
B = 14