Usually when you do expressions involving subtraction you can do Keep, Change ,Change That means you keep the sign of the first number and change the other two signs. It is best you rewrite the expression to addition because a lot of people don't do well with subtracting .
Okay so this is how i did it but idk if it’s right. so i multiples the top and bottom by square root of 3 to get rid of the square root of 3 then i was left with 8-1/2(1) and got 7/2