40 less than 10 times Diaz's age is 20 more than 10 times Sierra's age. If Sierra is currently 30 years old, how old will Diaz be 20 years from now? Think carefully first, then make a decision:
If Sierra is currently 30 years old, 10 times her age is 30 * 10 = 300. Twenty more than 10 times Sierra's age is 300 + 20 = 320. 320 is 40 less than ten times Diaz's age so 10 times Diaz's age is 320 + 40 = 360. If ten times Diaz's age is 360, Diaz is 360 / 10 = 36 years old. Twenty years from now, Diaz will be 20 + 36 = 56 years old. So, the answer is 56.