Question 84697
Let 'I' denote current, 'R' denote resistance and let "k" denote te constant of proportionality.

Given I is inversely proportional to R.

Then the equation would be I = k/R

 Given I = 80 when R = 30

==> 80 = k/30

==> k = 80*30

      = 2400 

Thus the equation becomes, I = 2400/R

Now given R = 12

So I = 2400/12

     = 200

Thus I = 200 amp when R is 12 ohms.

20) the equation that expresses the variation will be I = 2400/R

Good Luck