Is there an image of this or something? I’m not sure where S is supposed to be. Is S on the bottom of the box?
Pythagoras theorem is: a^2+b^2=c^2
If it is the bottom of the box you need, then:
a=15, b=4, c=x
15^2+4^2 = 241
c^2 = 241
c = √241
Which can either be written like that or is 15.5241747
Or
15.52 (2 d.p.)
Let me know if that’s the side it meant?
