The first step is to draw the starting material:
Next it is important to note the type of reaction which is elimination with ethoxide (a strong base and good nucleophile) which classifies it as an E2 reaction. The expected product is an alkene.
Once the reaction type has been noted and an idea of the type of product being generated has been thought through, it is important to classify the alpha-carbon and beta carbons from which elimination can occur. This starting material has two beta carbons from which elimination can occur, thus two products can be formed: one major and one minor (see the picture below). Finally the mechanism of the E2 reaction must be considered, it is concerted: the leaving group leaves and a double bond is formed in the same step and the product alkene is generated.
The reaction obeys Zaitsev's rule with the major product being, 2,3 dimethyl 2-butene (the more substituted alkene).