To find the answer we have to subtract 6 hours 45 minutes from 7 hours 15 minutes. As we see that 15 is less than 45, we turn 7 hours 15 minutes to 6 hours 75 minutes, and now we can subtract. 6 hours 75 minutes - 6 hours 45 minutes = 30 minutes. Now, we see that the answer is 30 minutes less sunlight.
Well we know that 1 inch is 2.54 cm. But how wide is .18? Lets do .18 x 2.54 to get 0.4572. Now lets add 2.54 + 0.4572 to get 2.9972. This means that the maximum width of the aorta is 2.9972 cm. Hope this helped :)