Answer:
9x - 1
Step-by-step explanation:
A triangle is a three-sided polygon with three edges and three vertices. the sum of angles in a triangle is 180 degrees
Area of a triangle = 1/2 x base x height
the perimeter of a triangle = sum of the side lengths
missing length = perimeter - sum of the two sides
sum of the two sides = (5x -1) + (2x + 5) = 7x + 4
missing length = 16x + 3 - (7x + 4) = 9x-1
