For this question, p and q are different (11 and 13). But shouldnt p and q, given that they are the diagonals of a rhombus, be equal to each other? Wouldn’t diagonals of a rhombus intersecting at 90 degrees be equal?
It is not true. The diagonals of the rhombus need not be equal. They are equal when a rhombus is a square. For a more detailed explanation you can watch this khan academy’s video that shows how rhombus diagonals are perpendicular bisector of each other - https://www.youtube.com/watch?v=_QTFeOvPcbY
This page provides more information on why diagonals of a rhombus are not equal in length- Why diagonals of rhombus are not equal? - GeeksforGeeks