Taking downward to be negative and to the right being positive.
The two vectors given represent the legs of a right triangle. The net force will be the hypotenuse of the triangle. The magnitude can be determined by the Pythagorian Theorem and the angle from the inv. Tangent
Fnet = sqrt(1.51^2 + 9.32^2)N = 9.44 N
theta = invTan(-9.32/1.51) = -80.8 degrees.
Fnet = 9.44N at 80.8 degrees below the horizon.
also. . . What is the direction of the net external force on the apple (measured from the downward vertical, so that the angle to the right of downward is positive)?
Answer in units of ◦