Given a math word problem, answer the following question. You might need to apply addition or subtraction mathematical operators on the numbers embedded in the text to answer the question and then only report the final numerical answer.

the map led them through the forest and into a cave . to open the cave doors they need to put weights on the switch . if the switch already has 234 lbs . of weights and the total needed is 712 lbs . how much more weight to they need to add ?
478

the elephant had 407 peanuts . she ate 129 of them . how many peanuts did the elephant have left ?
278

after a week sofia did a survey to ask if the students liked the new menu . she found out that 235 students liked the new menu while 165 did n't . how many students took part in sofia 's survey ?
400