Adding fractions w/ variables?

Question

x/a + y/b + z/c = 1

when i have to solve for a

Answer 1

first get the term with a in alone on one side of the equation:

x/a = 1 - y/b - z/c

multiply bopth sides by a

x = a(1 - y/b - z/c)

divide both sides by (1 - y/b - z/c) Note: onl true aslong as (1 - y/b - z/c) does not equal 0 as you can not divide by 0.

a = x/(1 - y/b - z/c)

a = x - xy/b - xz/c