The formula to find the volume multiplies the length by the width by the height.A cube has all edges the same length .If we multiply the edges three times we get the volume of any cube.
Volume of cube with sides a is Volume V= 
In the question the cube is having an edge of 3.4 meters
Volume V= 
Volume of cube is 39.3 cubic meters.
THE ANSWER IS THAT A= 1.25
There are 29 quarts of fruit punch in 7.25 gallons of fruit punch.
Large cab doors= 12.5x2.5= 31.25in
1feet = 12in
12feet X 12 = 144in board
144 / 31.25 = 4.608
4 large doors can be cut
19in left over