Respuesta :

savannahlynn07

Answer:

Jennifer is 15 and Zack is 6

Step-by-step explanation:

z+ (2z+3)=21

z+2z+3-3=21-3

z+2z=18

3z=18

3z/3=18/3

z=6

so plug 6 in for all the variables and their ages are

Zack-6

Jennifer-15