Those are 45-45-90 and 30-60-90 triangles.
for #4, you would divide your hypotenuse by root 2 (r2) to get 3 for your legs (X and Y)
For #5, you have to divide 9r3 by r3 to get to X, making X=9. Then you can multiple 9 by 2 to get Y, making Y=18
#6, you do the same as 5. You are starting on the short side, since it's across from the 30 degree angle. To get the other leg, you multiple 7 by r3, getting 7r3. To get your Hypotenuse, you multiply by 2 to get 14.
The picture below has the formula/relationships between the sides of the two types of triangles.