Answer:
Let width of rectangle be x cm.
3x+x+3x+x=39
8x=39
x=39÷8
=39/8
=4/7/8
3x=39/8×3
=117/8
=14/5/8
Hence, length=14/5/8cm while width=4/7/8cm.
Hope attachment helps (✿^‿^)
Answer:
The first one
Step-by-step explanation:
If you have any questions about the way I solved it, don't hesitate to ask me in the comments below ;)
Answer:

mass = 3.645 g
volume = 9×9×9
= 729 cm³
density = 3.645/729
= 0.005 gcm^-3
Step-by-step explanation:
the volume is 729 cm³ cause the given height is 9cm and it is a cube. cube has equal sides so their lengths are the same.
volume = length × height × width