[tex]\huge\textsf{Hey there!}[/tex]
[tex]\text{Usually when you have a variable by itself it’s usually understood to be an INVISIBLE ONE}[/tex]
[tex]\rm{d\timesd\times d \times d}[/tex]
[tex]\rm{= 1d\times 1d \times1d\times1d}[/tex]
[tex]\rm{= d^2 \times d^2}[/tex]
[tex]\rm{= d^{2\times2}}[/tex]
[tex]\rm{= d^4}[/tex]
[tex]\huge\boxed{\mathsf{Therefore, \ your \ answer \ should \ be: d^4}}\huge\checkmark[/tex]
[tex]\huge\text{Good luck on your assignment \& enjoy your day!}[/tex]
~[tex]\frak{Amphitrite1040:)}[/tex]
