Answer:
8a units (c)
Step-by-step explanation:
an octagon has 8 sides, and if each side is 'a' units, it means each side it equal. therefore, add 'a' 8 times.
this expression would be: a + a + a + a + a + a + a + a
OR, multiply 'a' by 8. --> 8(a)
understand that there is an invisible 1 before each 'a' variable. the coefficient for each 'a' is 1. therefore, when adding, it will be 1a + 1a, and so on.
therefore, you get 8a.
hope this helps!<3