Answer:
$42
Step-by-step explanation:
Any time you see units squared or to the power of two (in this case "square foot"), you know you'll be dealing with area.
So, really we want to start by finding the square footage, or area, of the bathroom mirror. We know it's a rectangle so we can use the area formula for a rectangle.
Area = L x W
L (length) = 3
W (width) = 2
Area = 3 x 2 = 6 feet^2
Since we know the mirror will cost $7 for 1 square foot, and we have 6 square feet, we can just multiply 6 x $7.
So the mirror will cost $42.