Your 3 variables in this equation would be:
x
x+1
x+2
as you need these numbers to be consecutive. Because it is asking for the sum, you need to add these three variables and set them equal to 138:
(x)+(x+1)+(x+2)=138
At this point the parentheses don't matter, so they can be removed:
x+x+1+x+2=138
Combine like terms:
3x+3=138
Subtract the three:
3x=135
Divide 135 by 3:
x=45
Then, plug 45 back into the other two variable equations:
45+1=46
45+2= 47
Your 3 consecutive integers are 45, 46, and 47