Question 1108343
A teacher
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teacher's age = t
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has two students, one two times as old as the other. 
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younger student's age = s
older student's age = 2s 
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The teacher is five times as old as the older student, 
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t = 5(2s)
t = 10s
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and in 5 years 
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teacher's age in 5 years = t+5
younger student's age in 5 years = s+5
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she will be five times as old as her younger student.
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t+5 = 5(s+5)

Using t = 10s, substitute 10s for t in

t+5 = 5(s+5)
10s+5 = 5(s+5)

Solve that for s, the age of the younger student.
Then substitute what you get for s in

t = 10s

That will be the teacher’s present age.

Edwin</pre>