Help with these words and expression Hello everyone! I need some help... I don´t know the meaning of: - slip on - plonk - working out problems Could somebody help me?

Informal letter to my friend, Alex Hi Alex! It was great to hear from you. I´m very happy for your good news. Congratulations for passing your exam and the prize, of course. I know you have been studying very hard the latest weeks. You really deserve it! Don´t worry I have a wonderful advice for you. I know you quite well and I´m sure you will be bored with the computer game in a few days after buying it. As well as this kind of games are expensive, in fact you can rent them when you want. Furthermore you have a game shop near your house where you can hire thousands of computer games. If I were you I´ll wait to save up little more and I´ll buy clothes. You must think summer is coming up and you are a very cool person. Surely you would like to buy new trousers, T-shirts, sundglasses and a outrageos swimsuit to be the most fashionable person on the beach. I hope I have helped you. Hope to hear from you soon and to know what you are going to do with your money. Cheers, Elisa