Step-by-step explanation:
[tex]( {m}^{15} )( {m}^{3} ) ^ {- 4} \\ = ( {m}^{15} )( {m}^{3 \times - 4} ) \\ = ( {m}^{15} )( {m}^{ - 12} ) \\ = {m}^{15 + ( - 12)} \\ = {m}^{15 - 12} \\ = {m}^{3} \\ {m}^{x} = {m}^{3} \\ x = 3[/tex]
