Michael is making a card for his dad's birthday. he's shaded a triangular section on the card where he wants to write his dad a message. what is the area of the parts of the card that are not shaded?
a) 144 sq cm
b) 108 sq cm
c) 72 sq cm
d) 36 sq cm
*if you do answer my question, could you tell me how and why that's your answer?

Option c) 72 cm²

Step-by-step explanation:

In the figure attached we can see a rectangle ABCD with length 12 cm and width 9 cm.

A  triangle PEF with height BE and base EF.

Since side AE = 3 cm, so side EB = EC = 9 - 3 = 6cm

and EF = AD = 12 cm

Now we will find the area of of the parts of the card that are not shaded.

Area of parts that are not shaded = Area of rectangle - area of shaded triangle

= (12×9) -

= 108 -

Option c) 72 cm² is the area of non shaded part.