Cyclohexanone is subjected to (i) $\mathrm{CH}{}_3\mathrm{MgBr}$, dry ether; (ii) $\mathrm{H}{}_3\mathrm{O}{}^{+}$; (iii) conc. $\mathrm{H}{}_2\mathrm{SO}{}_4$, heat. The major final product is

Step (i)-(ii) gives the tertiary alcohol 1-methylcyclohexan-1-ol. Acid-catalysed dehydration proceeds through the tertiary carbocation, and the more substituted (trisubstituted) alkene is the major product by Zaitsev's rule: 1-methylcyclohexene.