Let the first initial of their name represent the individual's age in years.
1) D = 3B ∴ B=1 or B=2 D=3 D=6
2) C = E+4 ∴ B=1 or B=2 or B=2 C=6 C=5 C=7 D=3 D=6 D=6 E=2 E=1 E=3
3) F > A > G ∴ A=5 or A=4 or A=4 B=1 B=2 B=2 C=6 C=5 C=7 D=3 D=6 D=6 E=2 E=1 E=3 F=7 F=7 F=5 G=4 G=3 G=1
4) A+G > F ∴, with 5+4 > 9 and 4+3=7 and 4+1=5, A=5 Angela is 5 years old B=1 Belinda is 1 year old C=6 Carl is 6 years old D=3 Deirdre is 3 years old E=2 Ethan is 2 years old F=7 Francine is 7 years old G=4 Gavin is 4 years old