19 just did this assignment on e2020
Answer:

Step-by-step explanation:
<u><em>Step 1:</em></u>

<u><em>Step 2:</em></u>

<u><em>Step 3:</em></u>

<u><em>Step 4:</em></u>
Adding
to both sides to complete the square

<u><em>Step 5:</em></u>

<u><em>Step 6:</em></u>
Taking square root on both sides

3 gardeners :90 minutes
? Gardeners : 15 minutes
1 gardener : 270 minutes
? Gardeners : 270/15
18 gardeners