The perimeter of a certain pentagon is 10.5 centimeters. four sides of this pentagon have the same length, in centimeters, h, and the other side has a length of 1.7 centimeters. what is the value of h?

The perimeter of a certain polygon is calculated by adding up the measures of all the sides. If we let h be the measure of the four other sides aside from the one already given, the equation would then become,
                                 P = 1.7 + 4h = 10.5
The value of h from the equation is equal to 2.2 cm. 

Where are the calculations?