4. Luke can purchase a 12-pound item from several

different retailers. Which of the following is the
best buy?
A Buy online for $15 plus pay shipping and
handling costs of $0.79 per pound.
B Buy online for $17 plus pay shipping and
handling costs of $0.69 per pound.
C Buy at a local store where the item’s price is
$24.99, and use a $3-off coupon.
D Buy at a local store where the item’s regular
price is $22.50 and it is on sale for 10% off.

3. Each year on the same day, Susan deposits $275
into a savings account that earns simple interest at
a rate of 4.5%. She makes no withdrawals. In 5
years, how much interest does the account earn?
A $12.38
B $61.90
C $99.01
D $185.64

I just need an equation for me to solve both of these questions please! Thanks!