X = number of cds on the rack
x + 7 = 30
x = 30 - 7
x = 23 <== so there are currently 23 cds on the rack
75/135 and 18/135
just times 9 and 15, 9 and 2, and then 15 and 5
Answer:
C should slot on top of A.
Then D should slot in next to C of the left.
Lastly B should be beneath D and on the left of A.
Hope that makes sense.