Ihave to build a box for my scouting project with a volume 36cubic centimeters. the base of the box 6cm long and 2m wide. how high should i build the box

To find volume you must take the width * the length * the height 
you know the length and width

6cm and 2cm and you know the volume which is 36 cm

the equation looks like (H = height)

6 x 2 x (H)/2 = 36/2

6 x (H)/6 = 18/6

H = 3