Let's first break it down to the time 8 people need for one wall. That would be 10 minutes, right? If one person would have to do it in stead of 8, you'd expect him to take 80 minutes.
To paint 7 walls, he would nee 7x80 = 560 minutes. 10 people would do that 10 times faster, ie., 56 minutes.
I know puzzles like these always have a mindtrick. Did I miss anything?? ;-)
First you add250+250 then you add 9+9 or you could do250×9 2 times then add them together . never mind just do 250×9 2times and that will eqaul 2,250 then add 2250+ 2250and you got the answer and the answer is 4500
You swap x and y. for example, the first set is (0,1) so the inverse would be (1,0)