Question 353251
Hello, 
Basically all it's calling for is to get R by itself on one side of the =. 
E/R+r =1, for R 
First we multiply by R to get it out of the denominator. 
E+rR =1R
Subtract E and R from both sides to get: (Note 1R is the same as R) 
rR-R=-E
rewrite as:
R(r-1)=-E
Now Divide by r-1 to get:
R=-E/(r-1)
Make sense?
RJ
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