Question 747235
Not sure what you mean with the "2 oz", but strictly as written, that is 2 of (1/16) of a pound, so you are indicating MASS, or "pounds", but not volume.  But whatever you mean, keeping in the same units, we can do this:


w = the "oz" of water to add

{{{highlight(2*99.98/(2+w)=90)}}}, which represents adding w "oz" to get 90% solution of DMSO.

{{{180+90w=2*99.98}}}
{{{90w=2*99.98-180}}}
{{{w=2*(99.98-90)/90}}}
{{{w=(99.98-90)/45}}}
{{{w=9.98/45}}}
{{{highlight(w=0.22)}}} oz