What can bias a scientists's observations

A bias is said to occur when a researcher influence the outcome of his experiments. Many things can bias a scientist observation.
A design bias may occur if the scientist did not take into consideration the inherent biases that are liable in the experiment he is performing.
Sampling bias may occur if the process of sapling introduces an inherent bias into the study; this may be in form of omission or inclusion.

the catch is that the top numbers are atomic masses the bottom numbers are the numbers of protons and electrons in an uncharged atom. they are the number of that atoms as you would find them on the periodic table. further, the numbers on the left are used to determine the missing numbers on the right

so here we go

atomic mass

239 + 1 = y + 134 + 3 combine like terms

240 = y + 137             subtract 137 from both terms

240 - 137 = y

103 = y

atomic number

94 = z +54 + 0

94 = z + 54               subtract 54 from both sides.

40 = z

answer

The answer to this problem is. 67