Answer:
[tex]\left(7+x\right)^{12}[/tex]
Step-by-step explanation:
[tex]\left\{\left(7+x\right)^4\right\}^3[/tex]
[tex]\left(\left(7+x\right)^4\right)^3[/tex]
Let's apply the exponent rule:
[tex]\left(\left(7+x\right)^4\right)^3=\left(7+x\right)^{4\times \:3}[/tex]
Multiply 4*3=12
[tex]\left(7+x\right)^{12}[/tex]
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Hope this helps!