The ratio for Friday to Saturday is 1 to 8. There were 7 total cars on Friday, and 56 on Saturday. 7 x 8 = 56, so that is how you get that ratio. Multiply 3 x 8 to fill in the blank for how many hybrid cars there were on Saturday. (24)
For Sunday, we know the three hybrid cars Friday Friday, and 27 hybrid cars from Sunday. 3×9 is 27, so you have to multiply the total number of cars from Friday, 7 x 9 to get the total number of cars for Sunday. (63)
The answer is 10 because the student student did not follow order of op. This means that the student added 25 and 5 together then dived that. However he should have divided 25 by 5 first and then added 5