3/4-1/4=
1/2+3/8=
6 1/2-2 1/2=
3 1/2-1 1/8=

1)  ½.

Explanation:

 3/4 − 1/4 = 2/4 = 1/2 ; or, ½ .

2)  ⅝ .

Explanation:
 
 1/2 + 1/8 = (1*4)/(2*4) + 1/8 = 4/8 + 1/8 = 5/8 ; or, ⅝ .

3) 4 .

Explanation:

6 ½ − 2 ½ = 4 .  (or; 6.5 − 2.5 = 4.0 = 4 .).

4) 2 ⅜ .

Explanation:

3 1/2 − 1 1/8  = ?
     
          → 1/2 = (1*4)/(2*4) = 4/8; → So rewrite: "3 1/2" as: "3 4/8"; and rewrite the problem:

          →  3 4/8 − 1 1/8  = 2 3/8 ; or, 2 ⅜ .
   

Reasons:
Reason 3: Congruent supplements theorem

Statements:
Statement 4: Angle 1 is congruent with angle 2

Option D:
Reason 3: Congruent supplements theorem.
Statement 4: Angle 1 is congruent with angle 2