the simplest thing to do is divide 63 by 3 (this gives the mean which will be the middle number of 3 consecutive integers)
63/3=21 is the age of the middle brother
the other brothers are 20 and 22
if you need algebraic work...
x+(x+1)+(x+2)=63
3x+3=63
3x=60
x=20
x+1=21
x+2=22