Answer:
[tex]\frac{(2-y)x}{5}\text{ litres}[/tex]
Step-by-step explanation:
Let l litre of 7 grams of salt per litre is combined with x litres of water which contains y grams of salt per litre to yield a solution with 2 grams of salt per litre.
Thus,
Salt in l litre + salt in x litre = salt in resultant mixture
7l + xy = 2(l +x)
7l + xy = 2l + 2x
7l - 2l = 2x - xy
5l = x(2-y)
[tex]\implies l =\frac{x(2-y)}{5}[/tex]
Hence, [tex]\frac{x(2-y)}{5}[/tex] litres of 7 gram of salt per litre is mixed.
