Answer: yes, Jenny is correct.
Explanation.
Analysis step by step.
1) Jenny's brother washed dishes 8 times.
2) Jenny washed dishes 4 * 8 = 32
3) The difference is 4 * 8 - 8 = (4 - 1) * 8 = 3*8 = 24.
4) Jeeny washed dishes 32 times, while her brother washed dishes 8 times, so, indeed, she washed 3 * 8 more dishes than her broter and she is correct.
You must realize that although she washed 4 times the number of dishes that her brother did, the difference is just 3 times: 32 - 8 = 24 = 3 * 8