Find the lcd for each pair of fractions

To find the LCD of your fractions ALWAYS remember as a last result multiply the denominators by each other.

LCD is basically which factors do they have in common.

2/7  and 4/5    is        7x5 =  35    LCD is 35  (because they are prime numbers)

5/6 and 4/9         3 can go in both numbers so multiply the first by 3 which is 
                           6x3=18, now can 9 go into 18? YES so 18 is the LCD

7/9 and 11/15     3 can go in both numbers but we are not going to multiply 
                           the first number instead multiply 15 x 3 which is 45, now 
                           can 9 go into 45? YES so the LCD is 45

1/12 and 3/9      Although 3 can go in both numbers if you have handy a 
                          multiplication table, one of the factors of 9 equals that of
                          12, 9x4 = 36 and 12x3 = 36, therefore LCD is 36.

Can you complete the rest from there? If not send me a message.