If it is 0.5 miles from the White House to the Washington Monument and 1.2 miles from the Washington Monument to the Capitol, how far is it from the White House to the Capitol?

There's no way to know the answer to this question without knowing where the monuments are located. For example, if the monument are all in a line, then it could like this:

White house Washington MonumentCapitol. The answer would then be 1.7.

But it could also look like this:

CapitalWhite houseWashington Monument. This would mean the answer would be 0.7.