10x10-5(300x2)/5 Ian theb jj

100 points, hi, i’m not sure how to get the equation from the graph and table.

Ageologist had two rocks on a scale that weighed 4.6 kilograms together. rock a was 0.5 of the total weight. how much did rock a weigh?

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