To find the missing angle in a triangle, you can use the fact that the sum of the angles in a triangle is always equal to 180 degrees.
Let’s denote the missing angle as \( x \).
You have the following angles in the triangle:
- Bottom left angle: \( x \)
- Top angle: \( 15^\circ \)
- Bottom right angle: \( 85^\circ \)
According to the triangle angle sum property:
\[ x + 15^\circ + 85^\circ = 180^\circ \]
Now, combine the known angles:
\[ x + 100^\circ = 180^\circ \]
Next, solve for \( x \):
\[ x = 180^\circ - 100^\circ \] \[ x = 80^\circ \]
So, the missing angle at the bottom left is \( 80^\circ \).