Sang Yu refers to the old man, not how old he is, but a name with a relatively large scope. Here are some poems about Sang Yu. I hope you can learn more.
I buried Baoyu in the poor spring, and I hung Sang Yu in the landscape. -Bai Juyi's Crying Liu Shangshu's Two Dreams;
I want to be close to Sang Yu in the next year. -Bai Juyi's "Baiyun Southbound Sending Tongzhou Yuanjiu Fenglizhou Yili";
Sang Yu sits at dusk, and the clock is leaking. -Bai Juyi's Yi Lao (Zhuang Ziyun: I live, I am old, I die);
On Sang Yu, the influence cannot be traced back. -Cao Zhi's "Giving a White Horse to Wang Biao";
Sunset enveloped Sang Yu, and there was a sense of loss. -Chang Jian's "Taigong Mourning for Late Encounter";
Lingbi Goose Water, Sang Yu Yanziliang. -Cao Xueqin's Goose Water;
The garden is full of geraniums and plants, and the trees around the house are Sang Yu. —— Chu Guangxi's Eight Poems of Tian Family (below);
Sang Yu is miserable and colorless, standing at dusk. -Chu Guangxi's Autumn Tour with Gentleman in Kunming Chisi Valley;
Andrew followed the light of clouds and mulberry trees. -Wei Yuan's "Guest Huai Ba Cambodian Gong Ding An Scheeren";
Sang Yu is ok, and I would like to send the word Acacia. -Han Yu, "Going to Que to Jiangzhou to Send Doctor Li from Hubei and Vietnam"
Sang Yu refers to old age, but at present he doesn't specifically mention how old he is. There are many poems about Sang Yu with different meanings.