Let one of the number be x.
The sum of the 2 number is 260
⇒ The other number is 260 - x
The number is 3 times the other
⇒ x = 3(260 - x)
Solve x:
x = 3(260 - x)
x = 780 - 3x
4x = 780
x = 195
x = 195
260 - x = 260 - 195 = 65
Answer: The numbers are 65 and 195.