ANSWER:
She should use 30 ounces of water and 180 ounces of 35% salt.
SOLUTION:
First, let us set up a table and fill in the unknowns with variables x and y.
component   Unit Value   Amount( ounces)  value
0% salt         0.0         x               0.0x=0
35% salt         0.35         y               0.35y
Total Mixture      0.3        210               0.3×210=63
From this, we can easily set up the two equations. Â
Sum of values of two salts = Value of mixture Â
0x+0.35y = 63 Â ................(1)
0.35y = 63 Â
[tex]y = \frac{63}{0.35}[/tex]
y = 180
Now,
Sum of amounts of each salt = Amount of mixture Â
x + y = 210 ---------> (2)
so, put y = 180 in (2)
x + 180 = 210 Â
x = 210 – 180 Â
x = 30
Hence, she should mix 30 ounces of water and 180 ounces of 35% salt.