IER - Solve For...

                 E
     I =       __
                 R

Look familiar? Solve for E? Solve for R? The answer is simple, if you think of a triangle...
                                  
                                      E

IR

(X)

Now, just cover up the letter you are asked to "solve for..." with your thumb and...presto...

1)     E = I x R

2)     R = E/I   (E divided by I)

3)     I =  E/R  (E divided by R)

Note: What throws a lot of people is that there is no numerical answer to this question. The answer isn't 4 or 2.6 or whatever. These questions look a lot harder than they really are.