What is this question asking and Help me solve this equation step by step Ok So I am about to take the accuplacer college level math for a college but I do not understand this problem on the practice packet. Honestly I am blank on this problem and need help step by step on how to solve it.Please help me understand it. Thanks in advance
If a ≠ b and 1/x
 + 
1/a= 
1/b
, then x =
A.
1/b
 – 
1/a
B. b – a
C.
1/ab
D.
a – b/ab
E.
ab/a – b
 A: It is asking you to solve for $x$, given that
$$\frac{1}{x} +\frac{1}{a}=\frac{1}{b}.$$
To solve for $x$, first isolate $x$ by itself on one side; for example, move that $\frac{1}{a}$ to the right. That will give you an equation of the form
$$\frac{1}{x} = \text{stuff}.$$
Do the operation on the right, and then take reciprocals (or cross-multiply) to get an expression for $x$ in terms of $a$ and $b$. Then figure out which of the five options given is that expression for $x$.
You can the work as an edit to your question and we can tell you if you are doing it right or not; that will help you learn better than me doing it for you. 
(For extra points, figure out exactly on which step you need to assume $a\neq b$...)
A: You need to solve the equation for $x$, but I imagine the fractions are throwing you off. You can get rid of the fractions by multiplying both sides by $abx$ (why? because this is the least common multiple of $a,b$, and $x$), then it's simple algebra to rearrange and solve for $x$. Do you see why it's necessary for $a\neq b$?
