Step-by-step explanation:
First find how many plants Samantha can plant in half an hour. To figure that out do 12 divided by 3 because in 1.5 hours she can plant 12 plants.
12÷3=4
Samantha can plant 4 plants in half an hour. Since 2.5 hours in 1 more hour than 1.5 hours multiply 4 by 2 to get the total amount she can plant in one hour.
4 x 2 = 8
Samantha can plant 8 plants in an hour. Now add 8 to 12 because 12 plants is 1.5 hours and 8 plants is 1 hour and 1.5 + 1 = 2.5 hours.
8 + 12 = 20.
Samantha can plant 20 plants in 2.5 hours.
