Turning effect of forces — practice question

A beam of uniform mass is supported at its midpoint and kept in balance by three weights, as illustrated. What is the value of distance $x$?

• A$17.5\,\text{cm}$
• B$22.5\,\text{cm}$
• C$35.0\,\text{cm}$
• D$37.5\,\text{cm}$