edit : the rest is zero : la console is right, but, after check : it's : 3x^2 + 13x + 4 .... and not + 5 (degree 0 term)
3x^3 - 2x^2 - 61x - 20 | x - 5 -3x^3+15x^2................3x^2 + 13x + 4 ........ 13x^2 - 61x -20 .........-13x^2 +65x ......................4x -20 .....................-4x +20 .............................0
finally :
(3x^3 - 2x^2 - 61x - 20) / (x - 5) = 3x^2 + 13x + 4
Hope this helps any sorry how its all scattered
-72 is the answer to this problem, hope it helps.