John M. answered • 01/22/18

Tutor

New to Wyzant
20+ Years Teaching College Anatomy & Physiology

Let's say there are a pounds of $5 coffee and b pounds of $3.20 coffee. Since there are two unknowns, we need two equations and they would be:

**5a + 3.20b = 4.55(26)**

**a + b = 26**

Solve for a and substitute

**a = 26 - b**

**5(26 - b) + 3.2b = 4.55(26)**

**130 - 5b + 3.2b = 118.3**

**-1.8b = -11.7**

**b = 6.5**

So we should use 6.5 pounds of the $3.20 per pound coffee. Now substitute 6.5 for b in one of the first two equations to find a, the amount of $5 per pound coffee to use.