Devaughn is 7 years older than Sydney. The sum of their ages is 89. What is Sydney's age?

The appalachian trail is a hiking trail that passes through the appalachian mountains. three members of a teen hiking group hiked a section of the trail. the hikers stopped at a rest area and equally shared 3 4 gallon of water. how much water did each person get?

Which shows the correct solution of the equation 1/2a+2/3b=50, when b=30?

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