譬如下面这句对吗?
Although she is 84 years, my mother is in excellent health.
虽然我妈妈已84岁高龄,但身体仍很健康。
不应省略 old,你的句子应改为:
Although she is 84 years old, my mother is in excellent health. 虽然我妈妈已84岁高龄,但身体仍很健康。
但可以将 old 改为 of age(较正式的使用方法)。如:
Although she is 84 years of age, my mother is in excellent health. 虽然我妈妈已84岁高龄,但身体仍很健康。