There are four known numbers, 7, 7, -3, 7.
Then 7+7-(-3)+7 equals 24.
Decomposition:
7+7= 14;
14-(-3)= 17;
17+7=24。
If the number provided by the author is a keyboard input error and the dot "."is a comma ",",that is, the original question is, 7.7, -3.7, how to make it equal to 24?
Addition and subtraction are as follows:
Analysis: Known 7.7, -3.7, equal result 24.
Suppose there is an unknown x in the middle,
Then 7.7-3.7+X=24
4+X=24
X=20