I believe you just plug in the distance formula:
[tex]25 = \sqrt{(y - 4) ^{2} + ( - 8 - 2) ^{2} } [/tex]
remove the radical by squaring both sides. then remove the exponents. you'll then have
[tex]25 = (y - 4) + ( - 8 - 2)[/tex]
[tex]25 = y - 4 - 10[/tex]
y equals 39. I'm not entirely sure about this. I hope I answered your question correctly
