Question

The sum of two numbers is 59 and the difference is 15 . what are the numbers?

Answer 1

Write a system of equation based on the number
For an instance, the two numbers are a and b.
"The sum of two numbers is 59" can be written as follows.
⇒ a + b = 59  (first equation)
"The difference is 15" can be written as follows.
⇒ a - b = 15  (second equation)

Solve the system of equation by elimination/substitution method.
First, eliminate b to find the value of a.
a + b = 59
a -  b = 15
--------------- + (add)
2a     = 74
  a     = 74/2
  a     = 37

Second, substitute 37 as a in one of the equations
a + b = 59
37 + b = 59
b = 59 - 37
b = 22

The numbers are 37 and 22