Decode the monkey's message by following the letter substitution rules on this fun worksheet.

To solve the problem, we need to decode the message Marvin the Monkey is trying to convey. The message is given as:

```
ZMO L
QMCAM
KMJMJM
RMJBLFQ?
```

We are provided with a set of rules for decoding the message. Let's apply these rules step by step.

Decoding Rules:

1. Change all of the Ms to As.
2. Change all of the Js to Ns.
3. Change the R to an S.
4. Change the A to a E.
5. Change the K to a B.
6. Change the B to a D.
7. Change the Z to a W.
8. Change the C to a V.
9. Change the L to a I.
10. Change all of the Fs to Cs.
11. Change the U to a W.
12. Change the Q to an H.

Step-by-Step Decoding:

#### First Line: `ZMO L`
- Z → W
- M → A
- O → O (no change)
- L → I

Result: `WAOI`

#### Second Line: `QMCAM`
- Q → H
- M → A
- C → V
- A → E
- M → A

Result: `HAVE`

#### Third Line: `KMJMJM`
- K → B
- M → A
- J → N
- M → A
- J → N
- M → A

Result: `BANANA`

#### Fourth Line: `RMJBLFQ?`
- R → S
- M → A
- J → N
- B → D
- L → I
- F → C
- Q → H
- ? → ? (no change)

Result: `SANDWICH?`

Final Decoded Message:

Combining all the decoded lines, the message reads:

```
WAOI HAVE BANANA SANDWICH?
```

This translates to:

```
WOAI HAVE BANANA SANDWICH?
```

Which can be interpreted as:

```
DO YOU HAVE BANANA SANDWICH?
```

Final Answer:

Marvin the Monkey is asking: "Do you have banana sandwich?"

$$
\boxed{\text{Do you have banana sandwich?}}
$$