the sum of three numbers is 70. one number is five more than a second number. it is also twice the third. find the numbers.

30, 25, and 15

Explanation:

Let the three numbers be a, b and c, so that a + b + c = 70

Because the first number is twice the third (and I am assuming that all three numbers are intergs), we can denote the first number by a =2k, the second by b = 2k-5 and the third by c = k

Then from your description

2k + (2k - 5) + k = 70

5k - 5 = 70

5k = 75

k = 15

2k = 30 2k-5 = 25

Hence the three numbers are a = 30, b = 25 and c = 15.

Hope this helps! :)