I don't know how to do fractions in complete sentences?

What is "doing fractions in complete sentences"?

Maybe it's as simple as reading the equation out loud. For example,
12/3 = 12÷3 "12 over 3 equals 12 divided by 3"
or
12/3 = 4 "12 over 3 equals 4"

Come to think of it, a complete sentence could just mean an equation.
Suppose a question asks "what is 5/10?"
You could write "1/2", but that's not a math "sentence". The complete "sentence" would be
5/10 = 1/2

Do you mean: equation ?

e.g. 1)
1/4 of 2/3 is what ?
1/4 x 2/3
= 1x2 / 4x3
= 2/12
= 2÷2 / 12÷2
= 1/6

e.g. 2)
what of 6 is 1/3 ?
6 x 1/3
= 6/3
= 2

e.g. 3)
8 of what is 1/4 ?
= 8 ÷ 1/4
= 8 x 4/1
= 32/1
= 32

I'm not sure what do you mean.

You'll have to be more specific. I have no idea what you're asking.