Question 757499
VARIABLES
L=30%
H=60%
T=50%
u=unknown amount of the 30% alcohol
v=40 liters of the 60% alcohol


{{{(Lu+Hv)/(u+v)=T}}}  Solve for u.


{{{Lu+Hv=Tu+Tv}}}
{{{Tu+Tv=Lu+Hv}}}
{{{Tu-Lu=Hv-Tv}}}
{{{u(T-L)=Hv-Tv}}}
{{{highlight(u=v(H-T)/(T-L))}}}


Substitute the known given values to find the value for u.