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.

[EX Q]: While on vacation , Haley took 50 pictures at the zoo and 8 at the museum . If she later deleted 38 of the pictures , how many pictures from her vacation did she still have ?
[EX A]: 20

[EX Q]: John needs $ 2.5 . He has $ 0.75 . How much more money does he need ?
[EX A]: 1.75

[EX Q]: Mary has 9 yellow marbles . Joan has 3 yellow marbles . How many yellow marbles do they have in all ?
[EX A]:
12