please help me with this quickly

Explanation:
We follow PEMDAS in reverse to undo every operation that is applied to variable x
Doing so will lead to the following
t = 0.4x + c
t - c = 0.4x
0.4x = t - c
x = (t - c)/(0.4)
The last equation is the same as writing [tex]x = \frac{t-c}{0.4}[/tex] which is what choice B shows.