Least Common Multiples and Least Common Denominator

What is the least common denominator of 2/6 and 7/8?

Which of these numbers could NOT be a common denominator for these two fractions?
1/6   and   1/4

Which of these numbers could NOT be a common denominator for these three fractions?
1/3   and 2/5   and   3/10

Find the least common denominator

(a)  

$$\frac{2}{3}\ +\frac{1}{4}$$   Find the least common denominator

(a)  

$$\frac{5}{8}+\frac{1}{6}$$   Find the least common denominator

(a)  

$$\frac{1}{2}+\frac{3}{7}$$   Find the least common denominator

(a)  

$$\frac{2}{9}+\frac{2}{3}$$   Find the least common denominator

(a)  

$$\frac{4}{5}-\frac{1}{10}$$   Find the least common denominator

(a)  

$$\frac{4}{9}-\frac{1}{6}$$   Find the least common denominator

(a)