Yiwu shengliang information consultation

When weighing drugs with a tray balance, the drugs should be placed on the left plate of the balance;

From the picture, the weight is 20g, and the scale indicated by the boarding code is 2.4g 。

∴ The mass of the tested drug is 20g+2.4g = 22.4g 。

So the answer is: left; ? 22.4.