Answer
17
Work Step by Step
$(x_{1},y_{1}) = (8,5)$ and $(x_{2},y_{2}) = (0,20)$
Then apply the distance formula ,ie,
$d = \sqrt {(x_{2}-x_{1})^{2}+(y_{2}-y_{1})^{2}}$
$d = \sqrt {(0-8)^{2}+(20-5)^{2}}$
$d = \sqrt {(-8)^{2}+(15)^{2}}$
$d = \sqrt {64+225} = \sqrt{289} = 17$
