new_contents: """
  Input:
  7/5+13/5
  
  output:
  4/1
  
  """
  
  import re
  
  def gcd(a, b):
  	if (a == 0):
  		return b;
  	return gcd(b % a, a);
  
  
  def lowest(den3, num3):
  
  	common_factor = gcd(num3, den3);
  
  	
  	den3 = int(den3 / common_factor);
  	num3 = int(num3 / common_factor);
  	print(num3, "/", den3,sep="");
  
  
  def addFraction(num1, den1, num2, den2):
  
  	den3 = gcd(den1, den2);
  	den3 = (den1 * den2) / den3;
  
  	num3 = ((num1) * (den3 / den1) +
  			(num2) * (den3 / den2));
  
  	lowest(den3, num3);
  
  
  print("write expression:")
  exp=input()
  array1 = re.findall(r'[0-9]+', exp)
  array=list(map(int, array1))
  addFraction(array[0], array[1], array[2], array[3]);
  
subject: Create Solve_and_reduce_expression.py