Cristel is five years younger than Monica. After 4 years, the sum of their ages is 27. How old are they now?

LET..

M AGE=X
C AGE=X-5
(X+4) +(X-5+4)=27
x+4+X-1=27
2X+3=27
2X=27-3=24
X=24/2=12
MONICA'S AGE=12
CRISTEL'AGE =X-5=12-5=7