What does the rational of property do

Find the solution of system of equation y= x-4 y=4x+2

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?

In a certain city, the hourly wage of workers on temporary employment contracts is normally distributed. the mean is $15 and the standard deviation is $3. what percentage of temporary workers earn less than $12 per hour? a. 6% b. 16% c. 26% d. 36%