Pls help

$2-(-7)$

Anything minus a negative is the same as adding them together, as two negatives cancel out.

$2-(-7)=2+7=9$

You should try to learn from this old post 

https://web2.0calc.com/questions/the-result-of-subtracting-a-negetive-integer-from-a-positive-integer-is-a-positve-integer