107 = 7 -2 (7b - 1)
First, distribute -2 to all terms within the parenthesis
-2(7b - 1) = -14b + 2
107 = 7 -14b + 2
Combine like terms
107 = -14b (+7 + 2)
107 = -14b + 9
Isolate the b. Note the equal sign, what you do to one side, you do to the other. Do the opposite of PEMDAS.
Subtract 9 from both sides
107 (-9) = -14b + 9 (-9)
107 - 9 = -14b
98 = -14b
Isolate the b. Divide -14 from both sides
(98)/-14 = (-14b)/-14
98/-14 = b
b = −7
-7 is your answer
hope this helps