SOLUTION: Mary and her brother John collect foreign coins. Mary has twice the number of coins that John has. Together they have 105 foreign coins. find how many coins Mary has.

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Question 492909: Mary and her brother John collect foreign coins. Mary has twice the number of coins that John has. Together they have 105 foreign coins. find how many coins Mary has.
Answer by Maths68(1474) About Me  (Show Source):
You can put this solution on YOUR website!
Let
John has = x coins
Mary has twice the number that John has = 2x
John's and Mary's coins together= 105
x+2x=105
3x=105
Divide by 3 both sides
3x/3=105/3
x=35
John has = x = 35 coins
Mary has twice the number that John has = 2x = 2*35=70