table, th, tr, td
n1 + n2 = n1 + n2
25 + 25 = 50
35 + 35 = 70
45 + 45 = 90
55 + 55 = 110

thead, tbody, tfoot
| | person 1 | person 2 | person 3
| exam 1 | 15 | 17 | 18
| exam 2 | 13 | 16 | 18
| exam 3 | 17 | 14 | 19
| average score | 15 | 15.66 | 18.33