Question 60255
Twenty years? Quite a long time. Anyway, in the problem you want to solve for x; you want to figure out what 'x' is equal to. In order to do this you must isolate the variable x. 
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Isolate The Variable X. Quite clearly we have to get rid of the -11 on the left hand side so that we're left with 'x' alone. To get rid of -11 we must make it equal to 0 (because zero is ... nothing). Now, -11 plus what is equal to 0? 
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Yup you must add 11 to the left hand side. But remember, what you do to one side, you must do to the other. So, you end up adding 11 to both sides.
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x - 11 + 11 = 5 + 11 (we add eleven to both sides)
x + 0 = 16 (we add the 'like terms' on each side)
x = 16 (since 0 is of no value we can ommit it, and we now know 'x')
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We can now go back and check if this works. Does substituting 'x' in our original equation for 16 give us the right answer?
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x - 11 = 5 
16 - 11 = 5
5 = 5
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Our answer is quite evidently correct. Hope this helped.