this is one question but with 3 parts; i answered 2 but i need one more.
part one: arif and keisha go to a restaurant. their meal cost 13.75. the sales tax is 5%
i got $0.69.
part two: they want to leave a 15% tip based on the bill and tax combined. i got $2.17
now the part 3 i need with says arif ordered a more expensive meal than keisha after tax and tip are figured he decides he should pay $3.00 more than keisha. how much should he pay?

After you (correctly) answered part-2, you knew the total bill . . .

             (13.75 + 5%) + 15% on top of that.

             (13.75) + (0.69)  + (2.17)  =  $16.60 .

If they split the bill equally, each would pay  (1/2) (16.60) =  $8.30 .

But Arif wants to pay $3 more than Keisha.

Just take $1.50 away from Keisha's half (leave $6.80),
and add it on to Arif's half (make it $9.80).  Then their
total is the same, but his share is $3 more than her share.

                        $9.80  +  $6.80  =  $16.60

                        $ 9.80  -  $6.80  =  $ 3.00  .