Jack and Jill collect ladybugs. Jack only collects the ones with 2 spots,
and Jill only collects the ones with 7 spots. Jack has 5 more ladybugs
than Jill. The total number of spots found on all of their ladybugs is 100.
How many ladybugs do they have in their combined collection?  Choose the correct choice from the following answers.
A) 17
B) 21
C) 23
D) 25
E) 35
If x is the number of ladybugs that Jack has and y is the number of ladybugs that Jill has, then   x − y = 5 and 2x + 7y = 100. Multiplying the first of these equations by 5 and the second by 2   and adding gives 9(x + y) = 225. Hence, x + y = 25.   correct answer 25
<result>D</result>
Jack and Jill collect ladybugs. Jack only collects the ones with 2 spots,
and Jill only collects the ones with 7 spots. Jack has 5 more ladybugs
than Jill. The total number of spots found on all of their ladybugs is 100.
How many ladybugs do they have in their combined collection?