For a reaction that proceeds by E1 mechanism, the rate determining step involves the formation of the carbocation.
The rate of formation of this carbocation depends only on the concentration of the t-butyl bromide since it is the only specie that enters into the rate equation.
Hence, when the concentration of t-butyl bromide is tripled, the rate of reaction is tripled.
Methanol does not enter into the rate equation hence doubling its concentration does not affect the rate of reaction.
When a solid substance is dissolved in a liquid such as water, the intermolecular forces of attraction between the molecules in the solid substance are overcome and they exist as ions in the solution. Hence the answer is 2.
