how do I insert a formula into Excel and number not disappear?

[Ruth]

I am using Excel and I am a novice. I am trying to type my formula in the
formula bar but then the number that I want to place in the cell disappears.
When I place the number in the cell, the formula disappears. Please help.

 

[Max]

I am using Excel and I am a novice. I am trying to type my formula in the
formula bar but then the number that I want to place in the cell disappears.
When I place the number in the cell, the formula disappears. Please help.

A cell can only contain either an input value or a formula, at any one time.
If you are entering source values in say A1 and B1, just use an adjacent cell
to house the formula, eg in C1. C1 could contain the formula, say:
=SUM(A1:B1)