Final answer:
To make one cell in Excel equal to another, enter '=' followed by the cell reference of the cell you want to match. Use multiplication or other operations combined with references to calculate values based on table data.
Step-by-step explanation:
To have one cell in Excel equal another, simply reference the other cell in the formula bar for the cell you want to contain the same value. For instance, if you want cell B1 to have the same value as A1, you would enter =A1 into cell B1. This creates a cell reference that links B1 to the value of A1. When A1's value changes, B1 will automatically update to match it.
If you are referencing values from a table similar to the one provided in the question, where you need to calculate something based on the data in the table, you'd use a combination of references and formulas. For example, if you want to multiply the Quantity of an element by its Average atomic mass, you could enter a formula in the Subtotal column. Assuming the Quantity is in B2 and the Average atomic mass is in D2, in cell F2 you could enter =B2*D2 to calculate the Subtotal for that element.