A sign in a local department store says, “All Items 30% off Marked Price.” Form a function and then use it to determine how much one has to pay for each of the following marked items: a $65 pair of shoes, a $48 pair of slacks, and a $15.50 belt.

f(x) = .70x

You are taking 30% off, and 100%-30% is 70%. So you just multiply x (which is the original price marked on the item) by .70. So the shoes would be 65(.70) the slacks would be 48(.70) and the belt would be 15.50(.70)