The poster is a parallelogram, and it's area is:
A = bh
A = 20 x 10
A = 200 in.^2
Note: ^2 after in. means squared for area.
The area of the triangle that Janelle cut out of the poster board is:
A = 1/2bh
A = 1/2 x 10 x 9
A = 90/2
A = 45 in.^2
The area of the poster board that she has left is: 200 - 45 = 155 in.^2
Answer: 155 in.
