What is the missing reason for the following proof?

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In simplified exponential notation, the expression a^2•a^-3•a 1/a 0

Write two subtraction equations that are equivalent to 5 + 12 = 17.

Ifurniture stores having a weekend sale and is offering 20% discount on patio chairs and table the sales tax on furniture is 6.25 using function composition how can you represent the total amount a that you would need to pay for this furniture that cost x dollars