So we know that the word 'product' means multiplication, and that means that h and 4 are being multiplied. Also, one-fifth of x is another way of saying that one-fifth is being multiplied with x. So then we can construct the equation:

And we can then simplify this by taking out the multiplication sign:

And so since we do not know what x or h is equal to, this is as far as we can go.
Since its not an even number it would be 432
(-2x + 4y)(3x - 7y) = -6x^2 - 28y^2 + 12yx
Assuming the garden is a rectangle, the area is equal to length times width.
So 20x = 760.
Divide both sides by 20.
x = 760/20 = 38 ft