This is a classic example of a \(3-4-5\) right angle triangle
The hypotenus is 5. If you use the Pythagoras theorem you will end up with hypotenus as \(5\)

At this point it is simple addition. x to y \(= 5\)
X to Z and from Z to Y = \(3+4 = 7\)
Hence \(7-5 =2\) is the difference in travelling from x to z and then to Y rather than going directly to y from x
option c