Question 14141
Write the equation like this

  {{{(6-3)/(3-2)}}} = {{{3/1}}} which is the ratio of quantity of the $2 mixture to the $6 mixture

Which means that in a 10lb mixture there is {{{3/4}}} of the $2 mixture which is = 7.5lb

leavin 2.5lb for the $6 mixture.

Check:
7.5lb of $2 mixture will give 2x7.5 = $15
2.5lb of $6 mixture will give 6x3.5 = $15

Sum total on L.H.S= 10lbs
on R.H.S = $30
which means that each lb will cost 30/10 = $3