Question

Observe following reactions and and arrange metals X, Y and Z in decreasing order of reactivity
YA+X → No reaction
YA+Z ZY+A
XB+Y → YB +X​

Answer 1

Y has displaced X in reaction I. So, Y is more reactive than X.

Z has displaced Y is reaction II. So, Z is more reactive than Y. 

Thus, Z is most reactive and X is the least reactive.