Joe: 7k
Jim: 7(k+1)
Jack: 7(k+2)
(7k-5) + (7(k+1) - 5) + (7(k+2) - 5) = 195
(7k-5) + (7k+2) + (7k +9) = 195
21k + 6 = 195
21k = 189
k = 9
Joe: 7k = 7(9) = 63
Jim: 7(k+1) = 7(9+1) = 7(10) = 70
Jack: 7(k+2) = 7(9+2) = 7(11) = 77
Answer: Joe=63kg, Jim=70kg, Jack=77kg