Answer:
the number of calculators that are neither scientific nor graphing is 20 - 18 = 2. So Yousif bought 2 calculators that were neither scientific calculators nor graphing calculators.
Explanation:
If Yousif bought 20 calculators, then the number of scientific calculators he bought is 40% of 20, which is (40/100) * 20 = 8.
The number of graphing calculators Yousif bought is half of 20, which is 20/2 = 10.
The number of calculators that are either scientific or graphing is the sum of the number of scientific calculators and the number of graphing calculators, which is 8 + 10 = 18.
Therefore, the number of calculators that are neither scientific nor graphing is 20 - 18 = 2. So Yousif bought 2 calculators that were neither scientific calculators nor graphing calculators.