The airmail rates to a country are shown.
Type | Mass | Cost |
Letters |
First 12 g | 20x¢ |
Every additional 6 g or less | 10x¢ | |
Postcards | Per piece | 40¢ |
Simon sent 3 postcards and a letter. The letter weighed 21 g. How much did Simon pay in total? Give your answer in terms of x in the simplest form.