The two methyl groups in methyl ethanoate are not equivalent to each other : one is attached to a carbonyl, the other to an oxygen atom. So there are two types of hydrogen in this molecule and we see two sets of peaks. Since neither methyl group has any neighbouring H atoms, each methyl group appears as a single line. Both peaks represent 3H atoms, so the integral ratio is 1:1 The -OCH3 group is at 3.66ppm due to the deshielding caused by the electronegative oxygen atom. The CH3C=O group is at 2.05ppm due to the slight deshielding caused by the carbonyl group.