fix syntax errors

app.py

@@ -20,16 +20,16 @@ def basic_calculator(num1:float, num2:float, act:str)-> float: #it's import to s
     try: 
         answer = 0
         action = ''
-        if act == '+' || act == 'add' || act == 'append' || act == 'plus':
+        if act == '+' or act == 'add' or act == 'append' or act == 'plus':
             answer = num1 + num2
             action = '+'
-        elif act == '-' || act == 'minus' || act = 'substract':
+        elif act == '-' or act == 'minus' or act == 'sub' or act = 'substract':
             answer = num1 - num2
             action = '-'
-        elif act == '*' || act == 'mul' || act == 'multiply':
+        elif act == '*' or act == 'mul' or act == 'multiply':
             answer = num1 * num2
             action = '*'
-        elif act == '/' || act == 'div' || act == 'divide':
+        elif act == '/' or act == 'div' or act == 'divide':
             answer = num1 / num2
             action = '/'
         else: