Answer:
m = 375 [gram]
Explanation:
A triple Beam balance is an instrument very easy to use, since we only have to perform the arithmetic sum of each of the weights that are recorded in each beam
m = 300 + 70 + 5 = 375 [gram]
For a better understanding, the following image is attached, with values on each beam, which should be read.
The largest mass is in the indicator of 100 [gram], the second mass is in the indicator of 20 [gram] and the third is in the indicator of 5.8 [gram]. Thus the arithmetic sum corresponds to:
M= 100 + 20 + 5.8 = 125.8 [gram]
Note: it is important that when the instrument is in balance, the opposite end of the beam should indicate a position of zeros.