Question 765964
#3(first) and #6 are the same general problem.  #3(second) is slightly different but still a related general problem, in that it uses TWO unknown numbers.


Some help for #3(second):


L = 0.16*16 (dollars per ounce)(ounce per pound)
H = 0.24 dollars per pound
T = 3.52 dollars per pound
u = pounds of peanut butter, UNKNOWN
v= pounds of jelly, UNKNOWN
M = 1.5 pounds of peanut butter & jelly mixture or combination


Watch carefully that units for the solution process have been changed to pounds, dollars, but you could convert to whichever units you need or want to work with.


Formulate the equations:

{{{(Lu+Hv)/M=T}}} and {{{u+v=M}}}
Remember, u and v are in POUNDS.  L and H and T are in dollars per pound.
Solve for u and v.


The process can continue like this,
{{{Lu+Hv=MT}}}, and maybe use the M equation as {{{v=M-u}}} and substitute.
{{{Lu+H(M-u)=MT}}}
{{{Lu+HM-Hu=MT}}}
{{{Lu-Hu=MT-HM}}}
{{{(L-H)u=MT-MH}}}
{{{u=(MT-MH)/(L-H)}}}
.
. and watch the signs carefully as you go.
.
continue..
.