Mathematics - Permutation & Combination Question with Solution | TestHub

Paragraph: Box $1$ contains three cards bearing numbers $1,2,3$; box $2$ contains five cards bearing numbers $1,2,3,4,5$; and box $3$ contains seven cards bearing numbers $1,2,3,4,5,6,7$. A card is drawn from each of the boxes. Let $x_i$ be the number on the card drawn from the $i^{th}$ box, $i=1,2,3$.
Question: The probability that $x_1,x_2,x_3$ are in an arithmetic progression, is