Question 909681
We know that the total cost  for the two mixes is $367.9
4.2*x+5.75*y=367.9
We know that the mix at $4.2 has 2 times the amount at $5.75
We substitute for x
4.2*(2*y)+5.75*y=367.9
We multiply out
(8.4+5.75)*y=367.9
We combine like terms.
14.15*y=367.9
Isolate y
y=   26.00
y=   26.00 at $5.75
Calculate x
x=2*y
x=   52.00 at $4.2
Your total for x  is    52.00
Your total for y is    26.00
Your total for x and y is    78.00
Total invested    52.00 +    26.00=   78.00
We check
4.2*   52.00+5.75*   26.00=367.9
  218.40+  149.50=367.9
367.9=367.9
Since this statement is TRUE and neither x nor y  is negative then all is well.