The first row of seating in section H of the Concert Area has 7 seats. In all, there are 25 rows of seats in section H, each row containing 2 seats more than the row preceding it. How many seats are in section H?

My attempt:

it is an arithmetic problem i guess.

a1=7

a1+(n-1)d

7+(25-1)2=55 seats

is this how you do this problem?