why it say no output..?

Question

num_1 ="5"
num_2 ="6"
total ="num_1 +num_2"
print = "total"

Answer 1

You need to call the print function, like this: print(total). Also, do not use quotes for the variables. I have changed your code, see below:
num_1=5
num_2=6
total =num_1+num_2
print(total)

Answer 2

also you defined 5 and 6 as strings so answer will be 56

Answer 3

the last line wrong... you should call print function..
total = num_1 + num_2
print (total)