a b/c
On a Casio calculator you can enter a fraction
ab/c
Example 1
To calculate with SET UP Input/Output Math
2 ab/c 4 EXE F↔D 0.5
or with SET UP Input/Output Line as
2 ab/c 4 EXE 2┘4 1┘2 F↔D 2┘4 0.5
Example 3
To calculate 
1 ab/c 2 ▷ + 1 · 6 EXE F↔D 2.1
Results of calculations that mix fraction and decimal values are always decimal.
Example 4
To calculate
1 ab/c 2 ▷ + 1 ab/c 3 EXE
Example 5
To calculate
1 ab/c 9 EXE × 9 EXE Ans×9 1
Example 6
To calculate 1 / 2 = 0.5
1 ab/c 2 EXE F↔D 0.5
Example 7
To convert the decimal fraction 2.5 into the improper fraction 5/2
2 · 5 EXE 2.5 F↔D 2.5 2.5
Be sure to select SET UP Frac Result d/c.
Example 8
To simplify
1 5 ab/c 6 0 EXE
Simp Ans►Simp
F=3,≣ EXE
Simp Ans►Simp
F=5,≣ EXE
Be sure to select SET UP Simplify Manual.