Answer
$-0.67\sigma$
$0$
$0.67\sigma$
Work Step by Step
The first quartile has an area of 0.25 to the left. Use a z-table (inverse mode), we can find $z\approx-0.67\sigma$
The median has an area of 0.5 to the left. Use a z-table (inverse mode), we can find $z=0$
The third quartile has an area of 0.75 to the left. Use a z-table (inverse mode), we can find $z\approx0.67\sigma$
