Okay then how about question 9:

I made a table of values:

Rectangle: [Area: 80] [Distance from AD: 4] [Distance from AB: 5]

Triangle: [Area: 9] [Distance from AD: 3] [Distance from AB: 3]

Lamina: [Area: 71] [Distance from AD: X bar] [Distance from AB: Y bar]

Then take moments: 71Xbar = 80x4 - 9x3 = 347, Xbar = 4.13 (2dp)

and for the other, 71Ybar = 80x5 - 9x3 = 373, Ybar = 5.25 (2dp)

I think I just realised that my answwers were wrong! I think I added when I should have subtracted. The angle therefore is wrong. Do you agree with this working?