Multiplying fractions is simple. You just multiply across so 7/3 x 2/3 is 14/9 and that is the simplest form.
Yes they do, Hope this helps :p
Use the chain rule.
Let u = 25sin²(x), such that dy/dx = dy/du · du/dx


I only know #1 which is 0.85
13: 72.25
14: 52
For 14, you need to split the figure into a triangle and rectangle.