If elsw

Question

int i=20;
if(i=10) // without == it is running successfully
Cout <<i;

The output comes out to be 10 but
How i=10 becomes true

Answer 1

Also, after assign, expression return assigned value (10). Then it will be converted from int to bool:
bool(10) == true

Answer 2

you are using the assignment operator =, you need to use the equality operator ==.
if (i==10)
cout<<i;

the difference
i=10;
i equals 10
assigns 10 to i;

i==10;
i is equal to ten
sees if the variable i is equal to the number 10