The expression you’ve mentioned, 10 5 3 20, appears to be a list of numbers rather than a standard mathematical expression. In mathematics, expressions typically include operators such as +, -, *, or / to denote calculations.
If you intended for these numbers to be operated upon, please clarify the operation you wish to perform. For example, if we were to assume simple addition, the expression would be interpreted as:
10 + 5 + 3 + 20, which equals 38.
If you meant something different or have specific operations in mind, please provide further details so that I can assist you accurately.