Question 240706
Let Alex = x
Let Alicia = x 
Since they are twins we can assign the same variable to both of them.
Let Kevin = x+5
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Since the sum of their ages is 53, the equation becomes:
{{{x+x+(x+5)=53}}}
Now, solve for x to find the twin ages.
{{{3x+5=53}}}
{{{3x=53-5}}}
{{{3x=48}}}
{{{x=48/3}}}
{{{x=16}}} ...this is how old each of the twins are.
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To find out Kevin's age, you would add 5 years.  {{{x+5=16+5=21}}}
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Done!  :)