
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 a magic square, the sum of the three entries in any row, column, or diagonal is the same value. The magic square below provides some numbers initially. Find $x$. 
[asy]
size(2cm);
for (int i=0; i<=3; ++i) draw((i,0)--(i,3)^^(0,i)--(3,i));
label("$x$",(0.5,2.5));label("$21$",(1.5,2.5));
label("$70$",(2.5,2.5));label("$7$",(0.5,1.5));
[/asy]

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