40% of
a number is 8 more than the
number
Which is the number

Do you mean 8 more smaller if so the answer to your question is
X+y=40
Y=8 + x
Substituting the second equation into the first:
X+(8+x)=40
2x+8=40
2x=32
Smaller number: x=16
Y=8+(16)
Large number: y=24