Answer:
64
Explanation:
Ok so I know I prolly didn't work this out the way they want you to, but this is how i have always done it and got the correct answer.
So, there are 180 degrees in a triangle right? Well, we know 2 angles, 65 and 51. So add them together and you get 116. Simply subtract 116 from 180 to find the missing angle.
65 + 51 = 116
180 - 116 = 64
m<PST = 64 degrees