Answer:
S=12+7D
Step-by-step explanation:
Linear relationships.
The initial amount of money Ethan has is $12. Each day, he adds up $7 to his savings. At a given day D after his initial funding, he will have added $7D, and he will have in his piggy bank
S=12+7D
For example, on the day D=30 he will have
S=12+7(30)=$222