％。
She owns 10% of the company's stock.
Literal
She [topic-は] that company's stock [object-を] 10 percent owns.
所有する ('to own / possess') is a formal Sino-Japanese verb fitting business and legal contexts; in casual speech you'd say 持っている ('have') to describe ownership of clothes or a car, but corporate shareholdings call for 所有. The number-percent expression １０％ is read 'じっパーセント' (or 'じゅっパーセント' in many speakers' usage) — the % symbol is read as the loanword パーセント, borrowed wholesale from English. The ~ている here marks ongoing state: 'is in a state of ownership'. The 株 ('shares, stock') is the same kanji as 株式 (stocks) and 株主 (shareholder).