I'm afraid you have typed "garbage in"
Your equations make no sense.
7E07X?
Usually E means exponent and 7E07 would = 7*10^7 might be a population 70,000,000, probably in 1800 but neither 7*10^(7X) nor (7E7)*X works.
2E doesn't work for E being an exponent.
x+1987 doesn't do anything. 1800+x could define x as being years after 1800
Please type the problem as it is in the book(?).
