Respuesta :

apologiabiology
B=ben age
D=daniel age

B is 3 times D
B=3D

B is 4 older than D
B=4+D

3D=B=4+D
3D=4+D
minus D both sides
2D=4
divide 2
D=2
sub

B=3D
B=3(2)
B=6

ben is 6 years old