Answer:
e) ab/(a - b)
Explanation:
1/x + 1/a = 1/b
now we need to transform this so that we get x = ...
first, let's multiply both sides by x
1 + x/a = x/b
now we subtract x/a from both sides
1 = x/b - x/a
we multiply both sides by a
a = ax/b - x
we multiply both sides by b
ab = ax - bx = x(a - b)
now we divide both sides by (a - b)
ab/(a - b) = x