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For (a), the answer is + 1 = + 1 = .
For (b), |x-5| given that x >= 5 is x-5 (by the definition of the absolute value)
For (c), |t-5| given that t < 5 is -(t-5), or 5-t. (by the definition of the absolute value)
Solved, answered and explained, in full.
As a prerequisite, you must know/read/understand the definition of the absolute value.
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Comment from student : Good reply. For part (a), the book's answer is -pi + 5. Does it matter if I write it as you did: 5 - pi?
My response : -pi+5 is the same (is equal to) 5-pi.
It is as clear as a sunny day, and any school student can confirm it . . .