The opposite angle is also 80°. since consecutive angles must total 180, the other 2 angles are 100 each. 100+100+80+80=360, as needed for a parallelogram
C) closest to 2/5.
2/3 is bigger than half 2/10 would be like less than 1/4
add 4 each time
the nth term is a_n or f(n)
the next term after that is a_{n+1} or f(n+1)
so each term is 4 more than previous
basically
a_{n+1}=4+a_n or
f(n+1)=4+f(n)
same thing
Your equation is correct.
