x= second number
x+5= first number
2(x+5)= third number
SOLVE FOR SECOND NUMBER
x + (x+5) + 2(x+5)= 75
multiply 2 by its parentheses
x + (x+5) + (2*x) + (2*5)= 75
x + (x+5) + 2x + 10= 75
combine like terms
4x + 15= 75
subtract 15 from both sides
4x= 60
divide both sides by 4
x= 15 second number
FIRST NUMBER
x + 5= 15 + 5= 20
THIRD NUMBER
2(x+5)= 2(15 + 5)= 2(20)= 40
CHECK
15 + 20 + 40= 75
15 + 60= 75
75= 75
ANSWER: The three numbers are 15, 20, 40
Hope this helps! :)