In a mathematical question it is stated as follows.
On Monday I sold 15 cows and today 5 more than on Monday. How many did I sell today?
The question is one of ambiguity. Does 5 more refer to a separate sale thus only the 5 or does more than mean a total of what is sold today and on Monday?
What would be the best way to phrase the question so that it clearly refers only to the 5 sold today.
You've misunderstood the question, perhaps because the repeated verb is elided. There weren't only five cows sold today, there were twenty. It's not "Today I sold 5 cows," it's "5 more than on Monday"
With the elision: On Monday I sold 15 cows and today [I sold] 5 more [cows] than [the number of cows I sold] on Monday. How many [cows] did I sell today?
On Monday I sold 15 cows and today 5 more than on Monday.
This one is absolutely clear. Today I sold five more cows than fifteen, that's twenty cows today.
On Monday I sold 15 cows and today 5 more.
This one is absolutely unclear. It could mean "today I sold a further five cows", that's five cows today. Or it could mean the same as the first sentence, twenty cows today. You should avoid sentences like this.
You can't. The number five is meaningless without being able refer to the original value of cows sold on Monday.
When the person says "5 more than on Monday", they are saying that 20 sold "today".
Cows sold on monday: 15
Cows sold today: 5 cows + cows sold on monday
20 total cows sold today = cows sold on monday (15) + five more cows (5)
When saying "5 more than" some value, we will always need to reference the value to "derive" the correct value.
The best way to cut ambiguity would be to simple say the actual value instead of saying it in a way where we would have to reference what we sold on Monday.
"I sold 15 cows on Monday and 20 today"
