Throwing in the parenthesis: ((3 factorial) + (4 factorial)) between: 10 and: 100. Otherwise it's just left to right processing: 3 + 4 * 10. Becomes 70

Throwing in the parenthesis: ((3 factorial) + (4 factorial)) between: 10 and: 100. Otherwise it's just left to right processing: 3 + 4 * 10. Becomes 70 as a consequence of these rules, the parser is pretty simple.