I recommend using desmos if you wanna know what a graph looks like !
Point a is at (-2,4) => (x1,y1)
Midpoint is (2.5, 3.5) => (a,b)
Point B is (x2, y2)
To find midpoint we use formula

a= 2.5, b= 3.5, x1= -2 and y1= 4
Plug in all the values and findout x2, y2

multiply 2 on both sides to remove fraction
(5 = -2+x2 , 7 = 4+ y2)
5 = -2+x2, so x2= 7
7 = 4+ y2, so y2= 3
The point B is ( 7, 3)
53×2=106
2×53=106
106×1=106
1×106=106
The volume of a rectangular prism is represented by the following equation:

where w is the width , l is the length, and h is the height
Replace
with
since the length is tripled


From this, we see that this new volume is 3x larger than the original. Thus, the volume is tripled when its length is tripled.
Let me know if you need any clarifications, thanks!