Inequalities

Which is larger cos(sin x) or sin(cos x) ? Does this depend on x ?

What fractions can you find between the square roots of 65 and 67?

Find all 3 digit numbers such that by adding the first digit, the square of the second and the cube of the third you get the original number, for example 1 + 3^2 + 5^3 = 135.

Find the positive integer solutions of the equation (1+1/a)(1+1/b)(1+1/c) = 2

Two cubes, each with integral side lengths, have a combined volume equal to the total of the lengths of their edges. How big are the cubes? [If you find a result by 'trial and error' you'll need to prove you have found all possible solutions.]