Answer:
35
Step-by-step explanation:
210/10=21 pens per friend
21+27=48 pens for benjamin
48-13=35 pens left
benjamin has 35 pens now
Note: a² - b² = (a-b)(a+b)
9x² - 16y² = (3x)² - (4y)² = (3x - 4y)(3x + 4y)
6.283 is your answer!
FORMULA: 2(pie)(radius)