Can anyone solve and explain part b

Below in bold.

Step-by-step explanation:

b.

If we drop a perpendicular line from B to AC and mark the point D on AC, we have 2 right triangles, with AD = DC = 16 cm.

So tan O = BD/16 = 15/8

BD = (16*15)/8

= 2*15

= 30.

So the area of triangle ABC = 16*30

= 480 cm^2.

answer: the common difference is -0.10

lockers 1, 4, 9, 16, 25, 40, and 49 are open

i ran through it by the other answer is wrong