Step-by-step explanation:
b = age of Bailey
c = age of Celine
b + c = x
c = b + 8
so, using that identity in the first equation
b + b + 8 = x
2b + 8 = x
or, to go "after" c (Celine) :
b = c - 8
c - 8 + c = x
2c - 8 = x
2c = x + 8
c = (x + 8)/2
in x years c will have increased to c+x, and b to b+x.
so,
b + x + c + x = x + 2x = 3x
and
2c - 8 = 3x
2c = 3x + 8
c = (3x + 8)/2