Answer :

heyDB
First number = X
Second number = 8X
Third number = X - 3  

The equation would be
X + (8X) + (X - 3) = 207 

X + (8X) + (X - 3) = 207

X + 8X + X - 3 = 207

10X - 3 = 207

10X = 207 + 3

10X = 210

X = 21

First number = 21
Second number = 8 * 21 = 168
Third number = 21 - 3 = 18