Question 1120803
x, volume of the 30% silver nitrate to add


{{{(0.3x+0.6*500)/(x+500)=0.5}}}


Simplify;

Solve for x.
Simple algebra.

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First two or three steps could be
{{{0.3x+0.6*500=0.5(x+500)}}}

{{{3x+6*500=5(x+500)}}}

{{{3x+3000=5x+2500}}}

and you can finish it.