Question 784430
Initially, {{{8*70/(8)=70}}} g/L


Boil off v liters of water to increase concentration:
{{{8*70/(8-v)=200}}} and solve for v.  
'
{{{8*70=(8-v)200}}}
{{{8-v=8*70/200}}}
{{{8-8*70/200=v}}}
{{{v=8(1-7/20)=8(20-7)/20=8*13/20=2*13/5=26/5}}}
{{{v=5&1/5 Liters}}}