Three hundred and ten million, seven hundred sixty-three thousand, one hundred and thirty-six
Do recall that squaring and the *radical sign* cancel each other out... like so:(

)

= a
When you put it that way, it isn't enough :P
(

)

= a
(

)

=?
so you start with
(

)

=

8x+1=25 <-- subtract 1 to both sides
8x=24 <- divide 8 to both sides
x= 3
To find out if it's an extraneous solution ask yourself: It mustn't result in a radical that I like to call... 'illegal'. Plug it into the radicand 8x+1 and make sure you get something that is not a negative number.... so, DO you get a negative number when you plug in x = 3 into the radicand?
(extraneous solution is a invalid solution)
x=3 not extraneous
The walls are vertical so the angle opposite X would be a right angle which is 90 degrees.
X would be 180 - 90 - 35 = 55 degrees
X and 2y - 5 are complementary angles which add together to equal 90:
2y - 5 + 55 = 90
Simplify:
2y +50 = 90
Subtract 50 from both sides:
2y = 40
Divide both sides by 2:
y = 20