Find the principal (positive)Square root of 14

(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

Can someone check if i did this right since i really want to make sure it’s correct. if you do you so much

If you answer 2+2 you will get over 80 points