a student bought some pens rupees 8 and some pencils at rupees 1.50 each. if the total number of pens and pencils is rupees 16 and thier cost is rupees 50, how many pens did he buy

A student bought some pens at RS 8 each and some pencils at RS 1.50 each. If the total number of pens and pencils purchased is 16 and their total cost is RS 50. How many pens did he buy.