In the central city grand prix, out of 30 cars that started the race, 12 of them finished. what percent of the cars finished the race? what percent did not finish the race?

To get the answer we can use proportion.
30100%
12x
Cross multiply now
30x=12*100%
30x=1200% /:30 (divide both sides by 30)
x=40% - it's the percentage of cars which finished the race.
100%-40%=60% - it's the answer

The internet will you

Yea they are simplyfiy the ratios