Question 838346
Use a ratio:
{{{ 5/8 = x/20 }}}
Multiply both sides by {{{ 8*20 }}}
{{{ 5*20 = 8x }}}
{{{ 8x = 100 }}}
{{{ x = 12.5 }}}
12.5 ounces of medicine needs to be 
added to 20 ounces of water