Welcome to the forum.
And if you are unfamiliar with posting code.
PLEASE ALWAYS USE CODE TAGS (the <> formatting button) when posting code.
It makes it easier to read your code and also easier to respond to your post.
Hint: You can edit your post, highlight your code and press the <> formatting button.
You can use the preview button at the bottom to see how it looks.
What you are asking for is what many have done before. Try a search here on "basic calculator".
Think about what you are being asked to do. You will need to input two numbers and an operator (+, - ,*, /, %), a switch/case will be useful.
Remember to initialize your variables when you define them. Always a good practice.
I will also mention that
using namespace std;
may be easy, but is a bad idea as it WILL
be a problem someday.
Work up some code and post it with any questions or problems that you have. Many here will help you understand what you are doing wrong. And I will do all I can to help you,but first I need to know what you have learned so far.
Hope that helps,