David W. answered 07/16/18
Tutor
4.7
(90)
Experienced Prof
"one number is x"
"Two numbers have a sum of 29" means:
"one number" + "other number" = 29
or
x + "other number" = 29
thus (subtracting x from both sides):
"other number" = 29 - x ["an algebraic expression in x"]