Whenever you are working with inequalities, you want to first isolate the variable by doing the inverse of what was already done.
42<-6d They have multiplied d by -6, so we have to divide both sides by -6. -6/-6=1. 42/-6 is -7. When you multiply/divide by a negative number, you have to flip the inequality sign. So we have -7<d, or d>-7. Flip the sign and you have d<-7, so your answer is A.
