Answer: 15,22 and 66
Step-by-step explanation: Call the numbers a,b and c.
Their sum is 103 so a+b+c=103
The second number is 7 more than the first so b=a+7
The third number = 3 times the second so c=3b
Now replace c with 3b in the top equation, so a+b+3b=103, which becomes a+4b=103
Now replace b with a+7, so a+4(a+7)=103. This solves to give a=15
b=a+7 so b=22 and c=3b so c=66