You are given a math word problem and you are supposed to apply addition or subtraction mathematical operators on the numbers embedded in the text to answer the following question and then only report the final numerical answer.

[Q]: When Jake had 1 cat , he needed to serve 0.5 can of cat food each day . Now that Jake has adopted a second cat , he needs to serve a total of 0.9 can each day . How much extra food is needed to feed the second cat ?
[A]: 0.4


[Q]: Oliver had 35 dollars . For his birthday he got 50 more dollars but spent 84 on a new game . How much money does he have now ?
[A]: 1


[Q]: Sally found 9 seashells , Tom found 7 seashells , and Jessica found 5 seashells on the beach . How many seashells did they find together ?
[A]:
21