I need help on this question, please.

Answer:
|X| = 72 cm
Explanation:
We need to find the magnitude of vector X.
Vector Y = 21 cm
Vector Z = 75 cm
We know that, the magnitude of resultant vector is given by :
[tex]Z={X^2+Y^2} \\\\X^2=Z^2-Y^2\\\\X^2=(75)^2-(21)^2\\\\X=72\ cm[/tex]
So, the value of magnitude of vector X is 72 cm