can someone show me an example of how to do this question

A hotel is in the shape of a  cylinder, with a circular foundation. The circumference of the foundation is 5 times the radius, increased by 72.96 ft. Find the radius of the circular foundation. Use 3.14 as an approximation for

piπ.

Circumference of the foundation is    5r + 72.96       (1)

And circumference is  given by    2 * 3.14 * r       (2)

Setting (1)  = (2)   we have that

5r  + 72.96   =  2 * 3.14 * r        simplify the right side

5r + 72.96  = 6.28 r          subtract 5r from  both sides

72.96  = 1.28r        divide both sides by  1.28

57  = r        [  i.e.....the radius is 57 ft  ]