Why is it important for the leading coefficient
to be nonzero?

Because if it is zero, then it is multiplied the variable and it will be zero.  For example if I had 0x(squared) + x, it would just be x because zero times any number is zero.  Looking at the problem, I would assume it was quadratic because it had x squared, but it isn't because there are 0 x squared values.

Step-by-step explanation:

c. 4 and 1/2 pounds is the answer! : )

so a parallelogram is just like a square base times height. multiply 40 and 39 to get 1560 inches.

a triangle is base times height divided by two. so multiply 7.9 and 5 and then divide it by 2 to get 19.75inches.

the kite can be split into two separate triangles and added together to get the total area. 30 x 4 /2 which equals 60. make sure to double it for the two triangles making 120.