Answer:
2
Step-by-step explanation:
[tex]( {4y}^{?} )^{3} = 64 {y}^{6} \\ \\ ( {4y}^{?} )^{3} = ( {4y}^{2} )^{3} \\ \\ {4y}^{?} ={4y}^{2} \\ \\ {y}^{?} ={y}^{2} \\ \\ ? = 2[/tex]
