Fractions, Simplify, Add, and Subtract

What number could be a common denominator for these three fractions?
1/2   and   1/3   and   1/4

• 9
• 8
• 12
• 6

3/4 + 2/8 = 

• 1
• 5/12
• 6/32
• 5/8

5/7 + 1/28 = 

• 6/35
• 12/196
• 21/28
• 1

6/7 - 2/3 =

• 32/21
• 4/21
• 1 3/21
• 7/21

7/2= what as a mixed number?

• 3  1/2
• 4  3/2
• 4  1/2
• 2  3/2

21/5= what as a mixed number?

• 5  1/5
• 4  2/5
• 4  1/5
• 5  4/5

Simplify  9/45

• 3/15
• 5
• 4
• 1/5

Convert Mixed Number to Improper Fraction
3 ⅓

• 12/3
• 7/3
• 10/3
• 31/3

Convert Mixed Number to Improper Fraction
5  ⅕

• 25/5
• 26/5
• 51/5
• 11/5

What is the difference?