The strategy that won't help her to calculate 9 - 7 is (a) Make 10
The given parameters are:
[tex]Yellow = 7[/tex]
[tex]Red = 9[/tex]
To determine 9 - 7,
- She can use addition, as in 9 + (-7)
- She can subtract directly by counting
However, she cannot make 10.
This is so, because 9 and 7 are not up to 10
Hence, the strategy that won't help her to calculate 9 - 7 is (a)
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