The question pertains to the angle property of a triangle.
The angle property of a triangle states that:
" The sum of all interior angles in a triangle is always equal to 180 degrees "
We will apply the angle property of the triangle and find the required numbered ( 1 ) interior angle in each figure.
The first figure delineates a triangular shape of a mountain. Where two of the interior angles made between the slant heights of the mountain and the ground are given as follows:

We will go ahead and express the angle property law of triangles in a mathematical form:

We will go ahead and manipulate the above equation and determine the angle ( < 1 ) as follows:

Hence, the required numbered interior angle for mountain figure is:

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The next figure models the triangular shape of the roof of a house. The interior angle formed between the slant heights of the roof and the horizontal base of the roof , and the vertex of the triangle is given as follows:

We will again apply the interior angle law for triangles which states:

We will go ahead and manipulate the above equation and determine the angle ( < 1 ) as follows:

Hence, the required numbered interior angle for house roof figure is:
