Can someone help me and explain me how you do this and not only give me the answer?

Alicia puts $400 in a bank account. each year the account earns 5% simple interest. how much money will be in her bank account in six months?

X+ y = 5 ; x - y =3 solve using linear combination

Check all that apply. f is a function. f is a one-to-one function. c is a function. c is a one-to-one function.