How to find distance and midpoint b\w the given points: a. (-3,-1)and(9,4) b.(3rs,-s2)and(rs,-r2) Find the length of given quadrilateral: (-8,-3),(-2,6),(8,5)and(2,-4)

I will do the first one, you do the second the same way

Distance between (a,b) and (c,d)
= √( (c-a)^2 + (d-b)^2 )

distance = √( (9+3)^2 + (4+1)^2 ) = √169 = 13

midpoint = ( (-3+9)/2 , (-1+4)/2 )
= (3,3/2)

By the "length" of the quadrilateral you probably meant the perimeter.
So just find the length of the 4 sides using the above formula, then add them up