How did the answer became 20

Question

>>> (-7 + 2) * (-4)
20

Answer 1

math
http://www.bbc.co.uk/bitesize/ks3/maths/number/negative_numbers/revision/4/

Answer 2

-7+2 = -5
-5 * -4 = 20

remember in multiplication:
- * - = +
- * + = -
+ * + = +
+ * - = -