What justifies the use of the normal distribution for the sampling distribution of the proportion?

Aclassmate thinks that solving a system by graphing gives an exact answer when the lines appear to cross at a grid point, but only an approximate answer when they don't. explain why this isn't true.

Can anyone explain to me how to do this? anything will .

Which of the following statements must be true about this diagram? check all that apply. x°, y°, z°, & w°