Hey please don't dlt and answer to the 6 and 7 no. Questions

Dear student,
7.

A D = D i a m e t e r = 30 c m C D = C h o r d = 24 c m x + y = 21 A g a i n, y^{2} + 12^{2} = 15^{2} \Rightarrow y^{2} = 15^{2} - 12^{2} \Rightarrow y^{2} = 81 \Rightarrow y = 9 x = 21 - 9 = 12 N o w, 12^{2} + a^{2} = 16^{2} a^{2} = 16^{2} - 12^{2} = 81 \Rightarrow a = 9 L e n g t h o f t h e c h o r d A B = 2 \times 9 = 18 c m

for other questions, start anew thread
regards