Find the square of the leg b of this right triangle: a=2b, c=10

Find a number such that if you add 8 and divide the result by 4 you will get the same answer as if you subtracted 3 from the original number and divided by 2

An arc subtends a central angle measuring 7pi/4 radians what fraction of the circumference is this arc?

Find the center and the radius of the circle with the equation: x^2-2x+y^2+4y+1=0?