Question

the sum of three numbers is 78. the third number is 2 times the second. the first number is 6 less than the second. what are the numbers

Answer 1

When we give x to second, then the third will be 2x and according to informations first one should be x-6. Then you have to sum all. It ll be equal to 4x-6.
78=4x-6
84=4x
21=x
So, first number is 15, second one is 21 and the last one is 42