I am not familiar with the way question 12 is worded, but I think you are supposed to use similarity of triangles to find the lengths of XY and YZ, which are half the lengths of AB and BC, respectively.

For the first question, it is important to remember that diagrams are not to scale. Since angles A measures 45 degrees and h is an altitude, intersecting AB at a 90 degree angle, angle AC(unnamed point where h intersects AB) is also 45 degrees. That makes the small triangle isosceles right triangle and h is the same length as 1/2 of AB. Use the Pythgorean Theorem or propetries of special right triangles to find the length of AC.