In this case we can apply a formula that tells us that:
# (AUB) = #A + #B - #AnB
Where A would be the ones who enjoy swimming and B would be the ones who enjoy running. AnB is the intersection of both sets, that is, those who enjoy doing both things, these values we have, if we replace them we have left:
#(AUB) = 80% + 70% - 55%
#(AUB) = 95%
Which means that 95% of people enjoy either swimming or running
