When I did it I got z=1.18 but its wrong and now I'm confused. P.s this might take me a while to understand.

the given equation is
8.3z - 4.1z + 4 = 14.5
4.2z + 4 = 14.5
4.2z = 14.5 - 4 = 10.5
4.2z = 10.5
z = 10.5/4.2
z= 2.5
so the answer is z = 2.5
is it given in the question
to inverse this ?
because i can only see the expression
so i solved according that