conversations.from: human
conversations.value: Kenneth spent 10% of this earnings this week on a new joystick. If he is left with $405, how much were his earnings?
  How to solve this?
conversations.from: assistant
conversations.value: Since Kenneth spent 10%, then he is left with 100% - 10% = 90% of his earnings.
  Since 90% of his earnings is worth $405, then 1% of his earnings is $405/90 = $4.50.
  Hence, Kenneth's earnings is $4.50 x 100 = $450.