Answer:
height of the pyramid is 7 feet.
surface area = B + 1/2
our equation will look like this do not mind the line at the end this'll be used in the final equation
51 ft² = 3ft^2 + 1/2 * 4 * 3ft * l
turn 3ft^2 into 9ft^2 then multiple 4 with 3ft then times with 1/2 this turns it into
51 ft^2 - 9 ft^2= 12ft/2 * l
42 ft² = 6 ft * I then we divide these two numbers 42 with 6 equaling 7ft!
