7+3x-12x=3x+1
We will first make all the numbers which have x in go to the left.
So 7+3x-12x-3x, we make the 3x negative since to make it move it needs to change.
Then we will make all the sevens go to the right, so 3x-12x-3x=1-7.
So now it is much easier to figure out.
-12x=-6
H = 70ft.
P = 35ft.
B = ?
H^2 = P^2 + B^2
70×70 = (35×35) + B^2
B^2 = 4900-1225
B = √3675
B = 35√3 ft.