The equation for the first club is:
y = 5x + 20 (where x is the number of hikes you go on)
The equation for the second club is:
y = 7x
By "economical", it means which club gives the best deal (meaning you not having to spend too much money). If we want to make the first club economical, we want to find how many hikes it takes to make the second club more expensive.
Let's make the two equations equal each other:
5x + 20 = 7x
Subtract 5x from both sides:
20 = 2x
Divide by 2:
x = 10
10 hikes is when the cost for each club is the same. Anything over that, then, makes the first club economical.
So, the answer would be:
x > 10
