Both systematic names are correct.

Isobutyl bromide is correct. The name 5-(3,3-dipropylmethyl)octane is incorrect and should be 4-ethyl-6-methyl-4-propylnonane.

Isobutyl bromide has a systematic name of 1-bromo-2-methylpropane. The name 5-(3,3-dipropylmethyl)octane is correct.

Both systematic names are incorrect. Isobutyl bromide has a systematic name of 1-bromo-2-methylpropane. The name 5-(3,3-dipropylmethyl)octane should be 4-ethyl-6-methyl-4-propylnonane.