Question 816382
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Hi,
Mary wants to make 10 qt. of a 63% saline solution 
by mixing together a 75% SALINE SOLUTION AND A 55% saline solution.
Let x and (10qt-x) represent the amount of 75% and 55% solutions respectively
 {{{75x + 55(10-x) = 63*10}}}    | After multiplying thru by 100
       20x = 80
         x = 4qt of 75% and 6qt of 55%   (10-4)
CHECKING our answer***
 {{{75*4 + 55*6 = 63*10 = 630}}}