Chapter 5 - Continuous Random Variables - Exercises 5.20 - 5.52 - Learning the Mechanics - Page 242: 5.34f

$p(76\leq x\leq 124)=.9974$

$z_0=\frac{x-\mu}{\sigma}=\frac{76-100}{8}=-3$ $z_0=\frac{x-\mu}{\sigma}=\frac{124-100}{8}=3$ According to table IV, page 773: $p(0\lt z\lt 3)=.4987$ $p(76\leq x\leq 124)=p(-3\leq z\leq 3)=2p(0\leq z\leq3)=2(.4987)=.9974$