Chapter 11 - Section 11.2 - Arithmetic and Geometric Sequences - Exercise Set - Page 647: 49

$a_{n}=4n+50$ $130 $ Seats

$54,58,62,...$ $a_{1}=54$ $d= 58-54=4$ $a_{n} = a_{1}+(n-1)d$ Substituting $a_{1} $ and $d$ values $a_{n} = 54+(n-1)4$ $a_{n} = 54+4n-4$ $a_{n} = 4n+50$ No. of seats in twentieth row $a_{20} = 4(20)+50$ $a_{20} = 80+50$ $a_{20} = 130$