Dont really understand can someone break it down please

Question

The height of a triangle is increasing at a rate of  centimeters/minute while the area of the triangle is increasing at a rate of  square centimeters per minute. At what rate is the base of the triangle changing when the height is  centimeters and the area is  square centimeters?

Remember that you're using the formula for the area of a triangle: Area = 

Answer 1

Area = (1/2) base * height

A = (1/2) B * h

dA/dt = (1/2) [ B * dh/dt + dB/dt * h]

dh/dt = 2.5, dA/dt = 5;

wish to find dB/dt

90 = (1/2)*B * 7.5

180 = 7.5 * B

1800 = 75B

B = 1800/75 = 24

5 = (1/2) [ 24 * 2.5 + dB/dt * 7.5 ]

10 = 60 + dB/dt* 7.5

-50 = 7.5 * dB/dt

-6 + 2/3 = dB/dt

Answer 2

If A = 1/2 bh, b= 2A/h

Thus, db/dt = (2h dA/dt - 2A dh/dt)/h²

h = 7.5

A = 90

dh/dt = 2.5

dA/dt = 5

Thus, db/dt = (2*7.5 * 5 - 2 * 90 * 2.5)/7.5² = -20/3 cm/sec or-6 2/3 cm/sec