First double the initial temperature: 40 degrees * 2 = <<40*2=80>>80 degrees
Then reduce that amount by 30 to reflect the dad's change: 80 degrees - 30 degrees = <<80-30=50>>50 degrees
Then multiply that number by 30% to find how much Jerry's mother reduces the temperature: 50 degrees * .3 = <<50*.3=15>>15 degrees
Now subtract 15 degrees from 50 degrees to find the temperature after the mother's change: 50 degrees - 15 degrees = <<50-15=35>>35 degrees
Finally, add 24 degrees to find the final temperature: 35 degrees + 24 degrees = <<35+24=59>>59 degrees
#### 59