A.

(1000-P)*(1+.015)=1000

=1015-P(1.015)=1000

=P(1.015)=15

P=14.78

This assumes that r is the montly interest rate. If that is the annual intererst rate then you would divide r by 12.

B.

(1000-P)*(1+.015)=P

=1015-P(1.0150=P

1015=P+1.015*p

1015=P(1+1.015)

P=503.72

Use this same logic to solve the following problems. I hope this helps.