1-Methylcyclohexene oxide (the epoxide of 1-methylcyclohexene) is treated with methanol containing a catalytic amount of $\mathrm{H}{}_2\mathrm{SO}{}_4$. Which product is formed mainly?

In acid the tertiary carbon (C-1, bearing methyl) has the larger partial positive charge, so methanol attacks there. The attack is from the face opposite to the epoxide oxygen (anti opening), so OMe at C-1 is trans to the OH produced at C-2. The product is trans-2-methoxy-2-methylcyclohexan-1-ol. Under basic conditions the regiochemistry would be reversed.