Determine B pls quickly!

Assuming the two horizontal legs are parallel, the smaller triangle is similar to the larger one, so that corresponding sides occur in a fixed ratio. In particular, you have

(6 cm) / (4 cm) = (6 cm + b) / (7 cm)

Solve for b :

(6 cm) • (7 cm) / (4 cm) = 6 cm + b

b = (6 cm) • (7 cm) / (4 cm) - 6 cm

b = 9/2 cm = 4.5 cm

step-by-step explanation:

x^2 -12x + 36 + y^2 = 36

x^2 + y^2 = 12x

r^2 = 12rcos(theta)

r = 12 cos(theta)