Solve for the indicated variable:

(x/a)+(y/b)+(z/c) = 1, for c

This is what I have so far:

z/c = 1-(x/a)-(y/b)
z/c = 1-[(xb-ay)/ab]

z/c=(ab/ab)-[(xb-ay)/ab]
z/c=(ab-xb-ay)/ab

...I'm not sure if it's right so far, and if it is, i don't know where to go after that. Help?

Thanks!

z/c=(ab/ab)-[(xb-ay)/ab]

z/c=(ab-xb-ay)/ab
sign wrong I think
z/c=(ab-xb+ay)/ab { - - is +}
c (ab-xb+ay) = a b z
c = a b z / (ab-xb+ay)