Hello from MrBillDoesMath!
Answer:
c = d/a + b
Discussion:
I think the Question is missing a comma. Assuming you are trying to find the value "c",
a(c-b) = d => divide both side by "a"
(c-b) = d/a => add "b" to both sides
c-b + b = d/a + b => as -b + b = 0
c = d/a + b
Thank you,
MrB