Which expression is equal to 2/sqrt7

(note i put the graph in so plz )the graph shows the amount of water that remains in a barrel after it begins to leak. the variable x represents the number of days that have passed since the barrel was filled, and y represents the number of gallons of water that remain in the barrel. what is the slope of the line

Find two rational expressions that have the difference of 2-n/n-4

Ineed to know the answer right now! !