Combo graph means two or more type graph at one graph or graph with secondary axis. secondary axis means graph based on another value rang in right axis. Following is the example of a two series line graph with secondary axis:

Following are the step by step procedure of How to make a two series line graph with secondary axis in excel:

Step-1: Open excel file. Input your data. Click to a blank cell. Now click to Insert tab & click to Line.

Step-2: Mouse right click to the blank graph. Click to the Select Data.

Step-5: Again click to Add.

Step-6: Again write the Series name. Select the Series values. Than click OK.

Step-7: From Horizontal (Category) Axis Labels click to Edit.

Step-8: Select the Axis label range. Than click OK.

Step-9: Click to OK.

Step-10: Mouse right click on graph and click to Change Chart Type.

Step-11: Click to Combo. Select two Chart type as Line. Give the tick mark at secondary Axis at Monthly efficiency Chart. Click to OK.

Step-12: Write click on a Line and select Add Data Labels to add data on top every Line.

Video:

How to make a two series line combo graph with secondary axis in excel: