def make_equation(coordinates, characters):
	"""
	Takes coordinates and characters and returns equation they make
	Sorts them in the right order depending on x coordinate
	:param coordinates: np.array
		(x,y) coordinates of characters
	:param characters: list
		list of characters
	:return equation: string
		equation made from characters
	"""
	# get x coordinates from tuples
	x_coordinates = [c[0] for c in coordinates]

	# pair them up with characters in a dictionary
	x_c_pairs = {x:c for x,c in zip(x_coordinates, characters)}

	# construct the equation by sorting x coordinates in ascending order
	equation = ""
	for x in sorted(x_c_pairs):
		equation += x_c_pairs[x] + ' '

	# remove the last space
	return equation[:-1]