Achemical change is a change in the of a substance.
a. composition
c. temperature
b. appearance
d. melting point

The answer should be composition because you are making a totally new substance when  you are changing it chemically. A physical change for example, would be cutting wood when in the end you still have wood. 

A chemical change is a change in the composition of a substance.

That is because it changes the bonds and how they form. 

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

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