Acarnival charges $7 for admission and $2 for each ride. an expression for the total cost of going to the carnival and riding n rides is 7 + 2n. how much is the total cost for 4 rides?

$7 is what you'll pay even if you don't ride any rides at all.  Each ride is an additional $2.  "n" is the number of rides, our unknown.  If we ride 4 rides, then n = 4.  Filling in our equation accordingly,  C(n) = 2(4)+7 which means that the cost for 4 rides is $15 (taking into account we are also paying admission.  The rides alone only cost 2(4) which is $8).

What are 5e numbers?