Answer: n = 70
Explanation:
The sum of all angles in a triangle is 180 degrees. We know this because the formula for degree measure in a polygon is (180) * (n-2) where n is the number of sides. (ie a square with 4 sides would have 360 total degrees because (180) * (4-2) = 360)
Given the angle of 40 degrees we know that the remaining angles need to add up to 140 degrees. because n = n we can say that 2n = 140 divide by 2 and get n=70