Do the values in the table represent a proportional relationship?

News cameras take an overhead picture of a crowd at an outdoor event journalist then count the total number of people in the picture and use the sample of estimate the total number of people in the crowd this process is an example of

When using the linear combination metho e linear combination method to solve a system of linear equations, the four options are:

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