I'm very lost on this, can I get some help? This should be easier than it actually is

You are at a restaurant and owe $38 for your meal. you want to leave a 20% tip. how much will your tip be?

Joel wants to buy a new tablet computer fram a store having a 20% off sale on all tablets. the tablet he wants has an original cost of $190. he also wants to make sure he has enough money to pay the 5% sales tax. part one joel uses the incorect expression 0.95(190)(0.8) to calculate that the tablet will cost him a total of $144.40. describe his error and write the correct expression part two how much will joel pay for the tablet show your work if you answer this question correctly you will receive a prize of 99 points good luck

Extra points! find the missing dimension! need asap