Assign the relative priorities of the two groups attached to each carbon. The two atoms directly attached to carbon-2 are C and H. Because C has a higher atomic number (6) than H (1), the CH_3 group is assigned the higher priority, as shown in the example for step 1. Now consider the groups attached to carbon-3. The example accompanying step 2 and rule 2 shows that ethyl has higher priority than methyl. The priority pattern is therefore as follows:

Because groups of like priority are on opposite sides of the double bond, this alkene is the E isomer; its complete name is (E)-3-methyl-2-pentene.