# Rearrange the formula

I need to rearrange this formula to make e the subject. Have I done it correctly?

10b + 5be - 3e + 7c
10b + 5be - 3e = 7c
5be - 3e = 7c - 10b
e(5b - 3) = 7c - 10b

e = 7c - 10b / 5b - 3

Mark44
Mentor
I need to rearrange this formula to make e the subject. Have I done it correctly?
You're not starting with an equation! Without the first line below being an equation, you can't solve for anything.
10b + 5be - 3e + 7c
10b + 5be - 3e = 7c
5be - 3e = 7c - 10b
e(5b - 3) = 7c - 10b

e = 7c - 10b / 5b - 3
Assuming that this is your starting equation -- 10b + 5be - 3e = 7c -- your work following it is fine, EXCEPT that you need to use parentheses. You should write e this way:
e = (7c - 10b) / (5b - 3)

Thanks a lot Mark

You're not starting with an equation! Without the first line below being an equation, you can't solve for anything.

Assuming that this is your starting equation -- 10b + 5be - 3e = 7c -- your work following it is fine, EXCEPT that you need to use parentheses. You should write e this way:
e = (7c - 10b) / (5b - 3)

Well if we assume that the first line is an equation (set equal to zero): 10b + 5be - 3e + 7c=0, then the second line changes:

10b + 5be - 3e = -7c, and that would change the rest of the steps which follow...