Question 1206851
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GOOGLE translation from Spanish


Help please I don't understand
Ali and Samuel both had the same amount of money after Samuel gave $15 to Ali. 
The ratio of Ali's money to Samuel's was 7:5. How much did each of them have at the beginning?
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<pre>
x = Ali's money at the beginning;
y = Sam's money at the beginning.


We have these two equations

    y - 15 = x + 15    (1)    "Ali and Samuel both had the same amount of money after Samuel gave $15 to Ali"

and 

    {{{x/y}}} = {{{7/5}}}    (2)    "The ratio of Ali's money to Samuel's was 7:5"


From (2),  x = {{{(7/5)*y}}}.  Substitute it into equation (1).  You will get

    y - 15 = {{{(7/5)y}}} + 15.


Multiply both sides by 5

    5y - 15*5 = 7y + 15*5

    5y - 75 = 7y + 75

    -75 - 75 = 7y - 5y

       -150  =    2y

          y  = {{{(-150)/2}}} = -75.


But this answer, y = -75, is mathematically non-sensical, since the amount of money must be positive, in this context.


It means that the problem, as it is given in the post, is posed INCORRECTLY.
</pre>

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Do not be surprised.


A significant amount of Math problems circulating in the Internet 
are posed incorrectly (an experimental fact). This is one of them.



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The solution, which @MathLover1 presented in her post, 
does not correspond to the given problem.


So, you better ignore it, for safety of your mind.