The assignment operations were not right, and have rectified the code. The invoking format was also not correct, as you require three arguments and the one you provided was a single variable with four values.
function [v,sa,p] = Rectangle(w,h,d)
v = volume(w,h,d);
sa = surface_area(w, h, d);
p = perimeter(w, h, d);
function v = volume(w, h, d)
v = w*h*d;
function sa = surface_area(w, h, d)
sa = 2*(w*d+h*d+h*w);
function p = perimeter(w, h, d)
p = 2*d + 2*w;
%to run the function use [v,sa,p] = Rectangle(1,2,3)
