For the first two use the formula 
Calculate 15 x 15 + 36 x 36 = 1521
Now its
1525 = C^2
Fins the squeare root of 1521 whitch is 39
and square c^2 as well whitch make it C^1 or simple C
This give us a final anwser of the missing side
39 = C
Second triangle
For this the formual is different since we are not finding the lenght of the hypotunus (C), we know this becauee the missing angle is met my a 90 digree angle.
Here the equasion is C^2 - A^2 = B^2
WE will it in again
15^2 - 9^2 = B^2
Calaulate 15 x 15 - 9 x 9 = 144
Now its 144 = B^2
Again we find the square root for each side
Square root of 144 is 12
and Square root of B^2 is Simpley B
We put in togethe to find the final anwser whitch is
12 = B
For the last two it is simple
<u>All angles of a triangle added together must always equal 180 degrees</u>
So it the two side are 75 and 32 we add them (75+32) to get 107
Now we just subtract that amount (107) form 180 to get the third missing angle. 180 - 107 = 73
Here the missing angle is 73
One way to know if this is correct is to add all side and see if it equaels 180
75 + 32 + 73 = 180
For the second question it seems to be exactly the same as the first in the photo so the anwser would also be 73.
Hope this helps! :)
