Answer:
Explanation:
Let's try each set of groups to see whether it equals 212121 cars.
3groups of 7 cars
7+7+7= 21, so jen can group her cars this way.
7 groups of cars
3+3+3+3+3+3+3= 21, so jen can group her cars this way.
4 groups of five cars
5+5+5+5 = 20, so jen cannot group her 21 cars this way.
2 groups of 10 cars
10+10 = 20, So jen cannot group her 21 cars this way.
Jen can groups her cars these ways:
. 3 groups of 7 cars
. 7 groups of 3 cars
Does this always work?