Well if he is filling one 3/4 quart bottle, then he must fill his measuring cup 3 times, so just multiply it by 5, and you have 15.
David needs to fill the measuring cup 15 times.
HI, I drew & explained it below. I used the sine trig function to find the diagonal length and then used the pythagorean to find the missing length. Hope this helps :)
Since you're adding x feet to the length which is 12 feet:
New area: (12+x)10.5
It’s 1, looks like you got it lol