How do I set the decimal places in TI 84 Plus calculator

SOURCE: comma key on TI-84 Plus Siver Edition calculator.

The comma key on the TI 84 SE is above the 7 key, and it is just left of (, right of x squared, and below SIN. thats where the "," key is. If you're asking something else, please clearify. My understanding is that you don't know where the comma key is. 

SOURCE: Find the antilog on the TI-84 Plus for finding pH in chemistry problems

I'm not specifically familiar with the TI83 or TI84 but I've used a lot of TI calculators in my time, so I'll give it a try. If your trying to find the antilog of a number in base 10 enter the number and hit the (10 to the X) button. If you're trying to find the antilog of a number in in base e (natural log), enter the number and hit the (e to the X) button.

SOURCE: No decimal display on TI BA-II calculator

Your BA II PLUS stores numeric values internally to an accuracy of 13 digits. However, the numbers it displays depends on the number of decimal places to which you have it set (choice of 0–9 or floating decimal). To set the number of decimal places displayed to three: hit [2ND][FORMAT][3][ENTER]This setting also continues indefinitely (even though the calculator is turned off and on) until it is changed.

SOURCE: how do I use the intersect function on the TI-84

1. You draw two or more graphs.
2. After the graphs are displayed, press [2nd][TRACE] to access the (CALC)ulate menu.
   
3. Select [5:Interesct]
4. You will be prompted for a first curve: the equation of the curve will be displayed at the top left corner of the screen. If it is one the intersecting curves, press [ENTER]
5. You will be prompted for the second curve. (You can move from one curve to another by pressing the UpArrow or DownArrow).
6. After two curves are selected, you will be prompted for a guess for the X-value of an intersection point: you can use the keypad to enter a guess or use the left or right arrow to move the cursor towards a point of your choosing (if there are more than one point).
7. After a short while the calculator gives you a solution.
8. If it fails, you must make a better guess.