i believe you can construct 2 quadrilaterals because you only need 2 right angles to make a square, once those two right angles are put together, you will now have 4 right angles. its kinda confusing but i hope this helped at all : )
They are any number in front of a variable so like 4x 7y or 8z. 4, 7 and 8 are the coefficients. A number by itself is a constant. For example 3, 1 and 9 are constants.