Step-by-step explanation: An operation must have some kind of mathematical 'action' going on. In this case, we see multiplication: the 6 is being multiplied by a and the product of 6 and a is being multiplied by b. We know this is multiplication because we can imagine multiplication symbols between the numbers; when a number and variable or variable and variable are next to each other, it means they are being multiplied.
Well let's see, how about we subtract 6 P.M from 30 minutes and that is 5:30 P.M then we subtract 5:30 by 15 minutes, and we get 5:15 P.M then we subtract 5:15 P.m by 45 minutes and we get 4:30 P.M
