Question

What is the answer to x ?

Answer 1

Because both angles are the same, and are in the same spot in the congruent triangles, we can set these angles up to equal each other:

$3x + 4 = 72 - x$

Add x to both sides:

$4x + 4 = 72$

Subtract 4 from both sides:

$4x = 68$

Divide both sides by 4 to get x by itself:

$x = 17$

The value of x is 17.

Answer 2

Judging by the question at hand I identified that both triangles are congruent, completely identical. 

I then next noticed that M<I and M<P are congruent angles.

So the equation you should have formed should be 
3x+4=72-x

The next step is to simplify the problem by first subtracting 4 from each side, to isolate the x, and then adding x to each side to isolate 68. The new equation should be 4x=68

Next just divide both sides by 4, and your solution should be x=17