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john is twice as old as edna, if edna is 12 years old how old john is?

Sagot :

Let x be the age of John
Let 12 be the age of Edna

Edna's age is two times the age of John.
John's age is twice as the age of Edna.

Then, the age of John is the age of Edna divided by 2.

12 / 2 = x
6 = x

So therefore, John is 6 years old, twice as old as Edna. 
let 'x' be John's age
let 'y' be Edna's age
----------
'john is twice as old as edna'
x = 2y ----equation 1
---------
'if edna is 12 years old'
y=12 -----equation 2
--------
substitute equation 2 to equation 1
x = 2y
x = 2(12)
x = 24
--------
therefore John is 24 years old