Question 1092167
Use the distance formula,
{{{7^2=(6-8)^2+(9-y)^2+(4-10)^2}}}
{{{49=4+36+(9-y)^2}}}
{{{(9-y)^2=9}}}
{{{9-y=0 +- 3}}}
{{{-y =-9 +- 3}}}
{{{-y=-6}}} and {{{-y=-12}}}
{{{y=6}}} and {{{y=12}}}
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{{{y=12}}}