Answer:
20x = 55
Step-by-step explanation:
First you have to add 3x to both sides of 11-3x=x

Now that you have 11 = 4x you divide 4 on both sides 
11/4 = x
But you can't divide 11 by 4 unless you are looking for the decimal form of 11/4 which is 2.75
so now we take 11/4 or 2.75 depending on if you need your answer in fraction or as a decimal and replace that with x however both will equal the number 55







The first case occurs in

for

and

. Extending the domain to account for all real

, we have this happening for

and

, where

.
The second case occurs in

when

, and extending to all reals we have

for

, i.e. any even multiple of

.