What is the chemical formula of the first carbohydrate molecule shown/?

You did not attach any diagram to your question, but you can use the details given here to determine the answer to your question.
Carbohydrates are made up of carbon, hydrogen and oxygen and the general formula for carbohydrates is CH20. The number of carbon atom that a carbohydrate have will determine the type of carbohydrate it is and its chemical formula. For instance, glucose has six carbon atoms and it is chemical formula is C6H12O6. Note that 2* the no of carbon will give you the number of hydrogen atoms.
To determine the chemical formula of the carbohydrate you are given, count the number of carbon atom in the carbohydrate and use the general formula for carbohydrate to write out its chemical formula.