Since you are not given the y-intercept, you have to solve for it through the equation, y = (4/5)x (which is the slope you are given) + b, and replace x and y with values given, which are (-5,-3)
y = (4/5)x + b
-3 = (4/5)(-5) + b
-3 = -4 + b
1 = b
Then replace b in the first equation to get the answer
25 feet above sea level means she travelled 25 feet to the surface of the sea. She would have to descend (37-25=12) 12 more feet to achieve 37 total feet of travel, so she descended 12 feet below sea level.
