Answer:
first = 21 - 5 = 16
second = 21
Third = 21*2 = 42
Step-by-step explanation:
first + second + third = 79
Let the second number = x
third = 2*x
first = x - 5
So we get
x - 5 + x + 2x = 79
4x - 5 = 79 Add 5
4x - 5 + 5 = 79 + 5 Combine
4x= 84 Divide by 4
4x/4 = 84/4
x = 21