In quadrilateral abcd, we have ab=3, bc=6, cd=4, and da=4. if the length of diagonal ac is an integer, what are all the possible values for ac? with a full explanation .

The triangle inequality applies.

In order for ACD to be a triangle, AC must lie between CD-DA=0 and CD+DA=8.

In order for ABD to be a triangle, AC must lie between BC-AB=3 and BC+AB=9.

The values common to both these restrictions are numbers between 3 and 8. Assuming we don't want the diagonal to be coincident with any sides, its integer length will be one of ...
  {4, 5, 6, 7}

A) for the n row: 22+(n-1)×6therefore,b) 100-22=78that means (n-1)×6=7878÷6=1313+1=1414th row has 100 seats