Answer:
In the Garden Club the cost will be a fixed fee of $25 and $10 for each rosebush, so if he buys X rosebushes, the total cost will be:
C1(X) = $25 + $10*X
While in the local nursery there is no initial cost, and each rosebush costs $15, so if he buys X rosebushes, the total cost will be:
C2(X) = $15*X
Now, let's find the value of X where C1 and C2 are equal, this is:
$25 + $10*X = $15*X
$25 = $15*X - $10*X = $5*X
X = 25/5 = 5
This means that if he buys 5 rosebushes, he will pay the same amount in both places.
If he buys less than 5 rosebushes, he will pay less in the local nursery (as it has a bigger slope, but no initial fee)
If he buys more than 5 rosebushes, he will pay less in the Garden club (because it has a smaller slope)
