Arithmetic Sequence Help

[icy timber]

Am I tripping or is there no arithmetic sequence to be found here? The following questions says to use the formula referencing this specific question c but i believe it was an error in the paper

[pastel gate]

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[haughty lake]

i believe it’s a typo

replacing 25 with 26 creates an arithmetic sequence

[icy timber]

exactly!

[haughty lake]

however, you are correct; the question is unsolvable in its current state

perhaps bring it up with your teacher?