Question 990613
x, quantity of type A coffee;
165-x, quantity of type B coffee;


Equation to Account for Cost of the Blend:
{{{(4.05x+5.45(165-x))=763.45}}}
You should be able to handle the arithmetic to solve for x, and then 165-x.


Concentration can be any unit of quantity per whole; it may be dollars per pound, or dollars per kilogram, or even parts per hundred  ( meaning, percent ).


A fully worked example, although using percent instead of price, is this video:
<a href="https://www.youtube.com/watch?v=-REjxT9KCzQ">two-part mixture percent using just one variable</a>