private static int indexOfSlash(String frac){
		int parDepth = 0;
		for(int i = 0; i < frac.length(); i++){
			//if it's a parentheses
			if(frac.charAt(i) == '(') parDepth++;
			else if (frac.charAt(i) == ')') parDepth--;
			//find the / if parDepth is 0
			else if (parDepth == 0 && frac.charAt(i) == '/'){
				return i;
			}
		}
		return -1;
	}