Let the $5.10 coffee be represented by x, and the $6.30 coffee be represented by y.
If she wishes to mix 40 pounds, this can be expressed as
[tex]x+y=40\text{ ----------(1)}[/tex]The total cost of both coffee is $222; this can be expressed as
[tex]5.1x+6.3y=222\text{ -----------(2)}[/tex]This provides a system of equations that can be solved simultaneously:
From equation 1, we can rewrite the equation to be
[tex]x=40-y\text{ ----------(3)}[/tex]Substitute equation 3 into equation 2:
[tex]5.1(40-y)+6.3y=222[/tex]Solving, we have
[tex]\begin{gathered} 204-5.1y+6.3y=222 \\ -5.1y+6.3y=222-204 \\ 1.2y=18 \\ y=15 \end{gathered}[/tex]To solve for x, substitute y = 15 into equation 3:
[tex]\begin{gathered} x=40-15 \\ x=25 \end{gathered}[/tex]Therefore, Jamila needs 25 pounds of the $5.10 coffee and 15 pounds of the $6.30 coffee.