In this task you will be given a list of lists, of numbers. For every inner list, you should multiply every number in that list and put the results in your answer. The output should be a list of numbers with the same length as the number of the lists in the input list.
[[3, -45, -28], [33, 4, -29, 13], [25, 6, 49, 38, 31], [23, 12]]