The balance is level. The yellow bag holds $x$ kg of rice and the grey weights are marked in kg. Which equation does the balance show, and what is $x$?

Add an equals sign and you have an **equation** — a question. 'For what value of $x$ does $2x+3$ equal 13?' is written $2x+3=13$. The **solution** is the value that makes the two sides equal. Here, $x=5$ works, because $2\times 5+3=13$. For Class 6, the simplest method is **trial-and-improvement** — try whole numbers until you find one that works. Faster algebraic methods come in Class 7.