Question 1197188
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Let x be the number of pounds of the $2 tea.

Then the number of pounds of the other tea is 40-x.


Write the total money equation

    2x + 5*((40-x) = 4.25*40 dollars.


Simplify and find x

    2x + 200 - 5x = 170

       -3x = 170 - 200 = -30

         x             = {{{(-30)/(-3)}}} = 10.


<U>ANSWER</U>.  10 pounds of the less expensive tea should be used.
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Solved.