Question

a*b=a+b+ab calculate 6*(-3)*7

Answer 1

first mistake: 6*(-3) = 6 +(-3) + (6*(-3)) = -3
It should be 6*(-3) = 6 +(-3) + (6*(-3)) = 6-3-18 = -15
Now proceed with
-15*7 = -15 + 7 + (-15)(7) = -15+7-105 = -113

Also, we don't know whether * is left- or right-associative. Right-associative would have been
6*[(-3)*7] = 6*[-3+7-21] = 6*(-17) = 6-17-6*17 = -113

Answer 2

First, calculate 6*(-3) = 6 +(-3) + (6*(-3)) = -3

Now, calculate -3*7 = -3 + 7 + (-3*7) = -21

Therefore, 6*(-3)*7 = -21

Answer 3

You are absolutely right, and I appreciate the clarification and correction. Thank you for pointing that out.

The correct calculation for 6*(-3)*7 is -113 as you have correctly demonstrated.