Question 893672
u = pounds of type A
v = pounds of type B
L = price for type A, $4.05 per pound
H = price for type B,  $5.55 per pound
C = cost of blend, $551.25
{{{v/u=4}}} for this month's blend


The ratio given means {{{v=4u}}}.


Account for cost, C.
{{{Lu+Hv=C}}}


Substitute for v.
{{{Lu+H(4u)=C}}}
{{{Lu+4Hu=C}}}
{{{(L+4H)u=C}}}
{{{highlight(u=C/(L+4H))}}}


Back to the formula for v,
{{{highlight(v=4C/(L+4H))}}}.


Solving all in symbols was neater, but you do not need to do this way all the time.  You now have the formulas for u and v and can just substitute the given values and compute.