Question 794648
The chemist should do this:

L = 30%
T = 54%
H = 90%
M = 400 ml.
u = unknown ml. volume of L
v = unknown ml. volume of H


{{{(Lu+Hv)/M}}} and {{{u+v=M}}}
and solve for u and v.


The chemist can then use the same formulas for any two-part mixture for other materials and with other given values.