Final answer:
The correct expression representing the total number of scales Ruben memorized is 8 + 4x, where he memorized 8 major scales in total and an unknown number x of minor scales per lesson for 4 lessons.
Step-by-step explanation:
The question is asking how to represent the total number of scales, both major and minor, that Ruben memorized over the course of 4 piano lessons last month. Given that he memorized 2 major scales per lesson and x minor scales per lesson, the total number of major scales he memorized is 4 times 2, which is 8. For minor scales, since we don't know how many he memorized per lesson, we represent it as x. He took 4 lessons, so the total number of minor scales memorized would be 4 times x, or 4x. The overall total for both major and minor scales is the sum of the two, which is 8 (from the 4 lessons of 2 major scales each) plus 4x (from the 4 lessons of x minor scales each). The expression that represents this total is 8 + 4x. Therefore, the correct answer is option C: 8 + 4x.