Is this answer ai generated

The expression in terms of D to show how much Billy would pay for the power tools is:
0.85D

The expression in terms of D to show how much Mark would pay in total if they buy the set of power tools is:
0.85D + (D + 15) + (D - 5)

The expression in terms of D to show how much Billy would pay in total if they buy the set of power tools is:
0.85D + (D + 15) + (D - 5)

Yes, it is possible that this answer was generated by an AI model.

Why do you think so

I apologize if my previous response was not clear. As an AI language model, I do not have the capability to directly analyze the source of the answer. However, based on the formatting and structure of the provided expressions, it is typical for AI models to generate equations or formulas in a similar manner. The use of variables (such as D) and arithmetic operations, along with parentheses to indicate order of operations, is commonly seen in AI-generated answers for mathematical expressions.

What does the expression 0.90 (D -5) refer to how do you know and how else can this expression be written

The expression 0.90(D - 5) refers to the amount of money saved by applying a discount on a quantity represented by D.

To understand this, we can break down the expression. (D - 5) represents the original quantity decreased by 5 units. Then, 0.90 is multiplied by the resulting value to calculate the discount, where 0.90 represents a 10% discount (as 1.0 - 0.10 = 0.90).

The expression could also be written as 0.9D - 4.5 in an expanded form, where the constant term (-5) is distributed across the multiplication and simplified to -4.5.

As an AI, I can explain how to determine if the answer is AI generated or not. In this case, understanding whether this answer is AI generated or not requires analyzing the content and context.

Based on the provided text, the expressions seem to represent the prices of power tools for Billy and Mark. The expressions are formed using mathematical operations, such as addition and subtraction, to calculate the total prices. These calculations are based on a variable 'D' which could represent the original price of the power tools.

Since these expressions involve arithmetic operations and a variable, it is possible that a human came up with them rather than AI-generated content.