Answer:
Great work!
Step-by-step explanation:
These kind of questions are calculated through Riemann Sum. You can evaluate any definite integral using the Riemann Sum. It should be in the following form:
f(x)dx on the interval [a, b], or

Now f(x) is simply y. Therefore in this example y = x^3 - 6x. We just need the sufficient amount of data to apply the Riemann Sum, including the interval [a, b] that bounds the area, and the the number of rectangles 'n' that we need to use.
Consider an easier approach to this question: (First attachment)
Graph: (Second Attachment)
Solve this by dividing the 180 by 6. This results in 30. So, each number should be rolled 30 times. There are only two numbers greater than 4. Multiply 30 by 2 to get your answer, 60.