What does it mean if a situation has a condition, or constraint? give an example.

In a math problem, it means the same as in real life. There are limits to what you can do, or range of values a variable may take on.

You cannot work more hours in a week than there are hours in a week. You cannot measure lengths less than 0, or time before the present. You cannot sensibly divide by zero. In general, you cannot use more resources than you have, or make use of them before they existed.

There are practical limits to size, speed, size of numbers,* and there are limits imposed by the laws of physics we recognize. (Objects can only be so big or so small or so many in the known universe, or within the confines of habitable portions of the Earth.)

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* The ratio of the size of the known universe to the size of the smallest describable object is less than 10^300. You can write numbers larger or smaller (than the inverse of this), but they have no practical meaning in our universe.

Two because two of one thing is two.