
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
In this expanded Number Wall, you add the numbers next to each other and write the sum in the block directly above the two numbers. Which number will be in the block labeled '$x$'? Modify the original layout to have four numbers at the base. [asy]
draw((0,0)--(10,0)--(10,2)--(0,2)--cycle);
draw((2,0)--(2,2));
draw((4,0)--(4,2));
draw((6,0)--(6,2));
draw((8,0)--(8,2));
draw((1,2)--(9,2)--(9,4)--(1,4)--cycle);
draw((3,2)--(3,4));
draw((5,2)--(5,4));
draw((7,2)--(7,4));
draw((2,4)--(2,6)--(8,6)--(8,4)--cycle);
draw((4,4)--(4,6));
draw((6,4)--(6,6));
draw((3,6)--(3,8)--(7,8)--(7,6));
draw((5,6)--(5,8));
label("$x$",(1,1));
label("4",(3,1));
label("8",(5,1));
label("7",(7,1));
label("11",(9,1));
label("$x+4$",(2,3));
label("12",(4,3));
label("15",(6,3));
label("18",(8,3));
label("",(3,5));  // This would be filled in the solution
label("",(5,5));
label("",(7,5));
label("",(5,7));  // This would be the top block with a number calculated based on x
[/asy]

Present the answer in LaTex format: \boxed{Your answer}
user