This is simple , minus 50 from 100 and that gives you 50 left . then divide that by 2 and that gives you 25 . so the minimum number of sales required is 25 . hope this helps :)<span />
Remember that exponentioal rule x^m times x^n=x^(m+n) therefor 7^4 times 7^-6=7^(4-6)=7^(-2) remember the other rule x^-m=1/(x^m) so 7^-2=1/(7^2)=1/49 answe ris A