The sum of two numbers is 136. one of the numbers is 51.what is the other number? what are the common factors of these two numbers.

The sum of two numbers is 136 (sum is what you get when you add two numbers together). If one of the two numbers is 51, and the other number is X, then:

X + 51 = 136

To solve for x we subtract both sides by 51. 

X + 51 -51 = 136 - 51
X = 85

The other number is 85. 

What are the common factors of these two numbers?
Factors are the numbers that multiply to make the product. 

Factors of 51: 1, 51, 3, 17
Factors of 85: 1, 85, 5, 17 

The common factors of these two numbers are 1 and 17.