Lizzy: Tom and Devin have been teaching for a total of 70 years. Devin has been teaching for 5 less than half the number of years that Tom has. How many years has Tom been teaching?.
Me: Hmmm, let me think. I think this is the detailed solution:
Let x be the number of years Tom has been teaching. Devin has been teaching for (1 / 2)x - 5 years. 70 = x + ((1 / 2)x - 5). 70 = (3 / 2)x - 5. 75 = (3 / 2)x. x = 50. Tom has been teaching for 50 years. Final answer: 50.