Answer
$x$ = $155.72$ words
Work Step by Step
$\mu$ =125, $\sigma$ = 24
i ) z- score corresponding to an area of 0.90 = 1.28
ii) Sub $\sigma = 24 , \mu= 125, z = 1.28$ into z = $\frac{x - \mu}{\sigma}$ and solve for x:
z = $\frac{x - \mu}{\sigma}$
$x$ = $\mu$ + $z\sigma$
$x$ = $125 + (1.28 \times 24)$
$x$ = $155.72$ words
