After subtracting 3 from 7, and dividing 4 by 2, you should end up with x=2.
Your answer would be the last option, c = √(E/m).
We can see this when we rearrange the equation, as:
E = mc²
÷ m
E/m = c²
√
√(E/m) = c
So you got all the steps in rearranging correct :)
I hope this helps!
3. 140 m^3
(3 x 6 x 7) + (1 x 2 x 7) = 126 + 14 = 140
4. 216 in^3
(4 x 4 x 9) + (3 x 4 x 6) = 144 + 72 = 216
