Your main choices here are (1) a calculator with statistical functions and (2) a table of z-scores.
(a) On my TI-83 Plus calculator I typed in normcdf(-1000, 0.92). The calculator returned the value 0.821. This is approx. 8/10 of the total area under the std normal curve.
(b) I typed in normcdf(-1000, -1.26) and got 0.104
(c) I typed in normcdf(-1000, -0.64) and got 0.261
(d) I typed in normcdf(-1000, -1.09) and got 0.138
since a² and b² are equal, you would do 13² plus 13² then add those and you end up with 338. then you find the square root of 338 which is 18.38477631, or 18.38
