Let [tex]\Phi(z)[/tex] denote the cumulative distribution function for the standard normal distribution (mean 0, standard deviation 1). Then you're looking for z such that
(a) [tex]\Phi(z) = P(Z\le z) = 0.70[/tex]
(b) [tex]\Phi(z) = P(Z\le z) = 0.40[/tex]
(c) [tex]\Phi(z) = P(Z\le z) = 0.25[/tex]
To get the corresponding z-score for each of 0.70, 0.40, and 0.25, take the inverse CDF of both sides:
(a) [tex]z = \Phi^{-1}(0.70) \approx 0.5244[/tex]
(b) [tex]z = \Phi^{-1}(0.40) \approx -0.2533[/tex]
(c) [tex]z = \Phi^{-1}(0.25) \approx -0.6745[/tex]
