To reduce the polygon count of a model with Blender 2.7:
1-Open the model with Blender then select the object polygon you want to lower.
2-From the menu panel, select the tool to access the modifier panel
3-Then, choose the “Decimate” tool
4-When the “Decimate” window appear, the polygon count is displayed
5-On the “Decimate” modifier window, change the ratio to a number lower than 1.00. For example
0.8 will reduce the polygon count to 80% of the original count.
6-The polygon count is now 80% of the original number.