Help plz I don't understand the last 2 questions

How are isotopes of the same chemical element alike? how are they different?

You exhale co2 which is produced during cellular respiration.  co2 combines with the water in your blood's plasma to make up one half of the body's most important buffer pair, carbonic acid.  the more physical activity you engage in, the more co2 your body is producing.  you can see this by putting some of the cabbage indicator in a glass and then blowing bubbles into it through a straw.  can you see a change in the color of the indicator?

When a device is used in a circuit in which the voltage is 81 v the current flowing through the device is 3 a what is the resistance of the device