Let first number be x. Then the second number is (6-x), according to the condition.
Then you have this equation
5x = 10*(6-x).
Simplify and solve
5x = 60 - 10x
5x + 10x = 60
x = 60/15 = 4.
ANSWER. First number is 4. Second number is (6-4) = 2.