# The professor's birthday

Professor of mathematics had 57 birthdays. The director congratulated him. The professor asked the director: "And how old are you?" The director replied: "I'm exactly twice as many years than you were when I was old as to you today."

How old is the director?

Correct result:

x =  19

#### Solution:

57+x=2y
y = 57-x
z = 57 + x

57+x=2•y
y = 57-x
z = 57 + x

x-2y = -57
x+y = 57
x-z = -57

x = 19
y = 38
z = 76

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