How much of a perfume that sells for $35 dollar per ounce should be mixed with a perfume that sells for $15 per ounce to make a 3-oz bottle of perfume that can be sold for $63? amount of $35 perfume=?

Let x be the amount of perfume at $15/oz and y be the amount at 35/oz, then
x + y = 3 oz
15x + 35y = 63 oz
solve first equation for x
x = 3 - y
substitute for x in second equation
15(3 - y) + 35y = 63
45 - 15y + 35y = 63
20y = 18
y = 0.9 oz
x = 2.1 oz
amount of $35 perfume = 0.9 oz