Mystery 2-digit numbers and systems of linear equations in three variables
There are three boxes to be added together to get 87.
The first box is ten more than the second and the
second is ten more than the third.
_ + _ + _ = 87
Let x be the first number
Let y be the second number
Let z be the third number
Then, we get the following 3 equations
x + y + z = 87 (1)
x = y + 10 (2)
y = z + 10 (3)
Using (3), we get z = y - 10
Substitute y - 10 for z and y + 10 for x in (1)
y + 10 + y + y - 10 = 87
3y = 87
y = 29
z = y - 10 = 29 - 10 = 19
x = y + 10 = 29 + 10 = 39
Therefore, 39 + 29 + 19 = 87
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Nov 21, 19 02:38 PM
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