Question 896214
L=7
H=23
T=15
M=128 but you must understand this is NOT OUNCES.  Why?  It is something else.
u = unknown amount of 7%
v = unknown amount of 23%


A unit conversion may be needed; but if you are justified in ignoring it,


{{{(Lu+Hv)/M=T}}} and {{{u+v=128}}}


A lesson for this in general is here:  <a href="http://www.algebra.com/my/Mixtures%3A-All-in-Symbols.lesson?content_action=show_dev">Mixing two concentrations for known amount of mixture - http://www.algebra.com/my/Mixtures%3A-All-in-Symbols.lesson?content_action=show_dev</a>