Final answer:
In Devin's lawn-care service charge expression, the fixed amounts 15 and 10 represent potential parts of the mowing charge. However, without additional context, it is not possible to definitively identify which part is correct.
Step-by-step explanation:
The part of the expression 15 + 2xy + 10 + (2x + 2y) that represents the charge for the mowing in Devin's lawn-care service is likely intended to be a fixed amount, separate from the variables that would denote the area of the lawn (x and y) or the number of hours worked. The fixed charges in the expression are the numbers without any variables attached, which are 15 and 10. Considering that lawn-care services typically have a starting charge or a flat rate for mowing a lawn, it is reasonable to conclude that both 15 and 10 could be part of the mowing charge. However, since the question explicitly asks for the part that represents the charge for mowing, we would select the option that best fits the context provided, which would usually be a singular charge rather than the sum of two separate numbers unless specified otherwise.