Question

P = a + (n - 1)b, for b

Answer 1

The answer is b=P-a-(n+1) all you had to do was the a and the parenthesis from the b and put it on the other side

Answer 2

P = a + (n - 1)b Subtratc a from both sides
P - a = (n - 1)b Divide both sides by (n - 1)

`(P - a)/(n - 1)` = b Switch the sides to make it easier to read
b =
`(P - a)/(n - 1)`