Question

The sum of three consecutive numbers is 243. What is the third number?

Answer 1

Three consecutive numbers can be written as x, x+1, and x+2, but they also can be written x, x-1, and x-2 where x is the biggest number.

sum means adding... so

$x + x - 1 + x - 2 = 243$
combine like terms and solve for x!