The number is 15,
I really don’t know if there’s such a strategy to find this out, I just used trial & error:
(a*4)+(a*3)=35
(5*4)+(5*3)=35
20+15=35
I think....
x is the radius of your circle
x+7 is going to be your hypotenuse
that’s all i remember
Well you can use the Pythagorean Theorem Formula a

+b

=c

. Just plug in the first 2 least numbers into a and b, and see if your answer(c) is equal to the last number. Hope I helped!
Since you requested I answer this, I will do my best, but I'm not sure I can explain it well.
45° clockwise from due east is just 45° from the east. Moving clockwise, which is the direction the hands of a clock move, you're going to the south, and since it's by 45°, you're halfway between east and south, so you're southeast.
The equivalent number is 9013