Question 53063
Try this:
Let x = the number of pounds of coffee @ $5.50 per pound and (40-x) the number of pounds of coffee @ $3.00 per pound. You can set up the equation as follows:
x($5.50)+(40-x)($3.00) = 40($4.00) Simplify and solve for x.
5.5x+120-3x = 160 Combine like-terms.
2.5x+120 = 160 Subtract 120 from both sides of the equation.
2.5x = 40 Divide both sides by 2.5
x = 16

The merchant should mix 16 pounds of the $5.50 coffee beans with 24 (40-16) pounds of the $3.00 coffee beans to obtain 40 pounds of $4.00 coffee beans.