i can use this like a t-84 calculator ?

Use the  " / "  symbol for the fraction bar.

For example, to do:     \(\frac25\)

Type:                           2/5

If the numerator or denominator contains another operation, you might need to put parenthesees around it. Make sure the fraction displays how you want at the top.  

I agree, but I always put parentheses around mine, especially when you get to the complicated order of operations topics and pre-algebra and above that.