Avideo game club charges a fixed annual membership fee of $18 and $3 per video game rented. let f(n) represent the total annual cost of renting n video games. which of the following functions best represents the relationship between f(n) and n if the membership was increased by $20 the next year?

Since there is a flat membership fee of $18, the y intercept is 18.  And since there is a $3 fee per number of video games rented, n, the slope or rate of change of the linear equation is 3.  The slope-intercept form of a line is:

f(x)=mx+b, where m=slope and b=y-intercept so in terms of n, games rented, the cost, f(n) is:

f(n)=3n+18