1/(x+a) - 1/(x+b) = 1/a x 1/b
First, rewrite this as 1/(x+a) - 1/(x+b) = (1/a)(1/b) (do not use "x" to indicate mult.)
Then the LCD is (x+a)(x+b)(ab)
so the first term becomes (x+b)(ab), and
the second becomes (x+a)(ab), and
the third becomes (x+a)(x+b).
Thus, we now have (x+b)(ab) - (x+a)(ab) = (x+a)(x+b)(b) + (x+a)(x+b)(a).
Now, with the fractions gone, can you solve thios for x?