In ΔDEF, the measure of ∠F=90°, FD = 3.3 feet, and DE = 3.9 feet. Find the measure of ∠D to the nearest degree

Lindsay used two points, (x, y; ) and (+2.82), to find the equation of the line, y = mx + b, that passes through the points. y2-y, first, she used the definition of slope and determined that the value of mis x, - . given this information, which expression must represent the value of b?