In #4, the joke is about how easy it is to spell the word, “ART.” It is easier than actually making it, like painting, sculpting, etc.

#5 is an insult from the woman on the left about what the woman on the right is painting. The woman in the left looks like an older version of the pretentious woman in cartoon #2, so that explains her assessment. She no doubt knows nothing about art other than how to spell it.