Here is your solution.. hope it helps
 
        
        
        
Answer: a) -7/12 ft/s, -20 ft/s, -7 ft/s
               b) 527/24 Ft²/s
               c) 2/25 rad/sec
Step-by-step explanation:
a) b=7 ; a^2+b^2 = 25^2
              a^2+b^2 = 625
Differentiate w.r.t = 2a (da/dt) + 2b ( db/dt) = 0 
                                     
As found from above put a=24 b=7,15 and 24. You will get the reuqired answer.
b) Area of the triangle = 1/2 * b*h
differentiate wrt to time leads to the following relation:

c) sin (Θ) = b/25
differentiate it again to give 

                                  
                                 
 
        
             
        
        
        
5w-3 > -29
Add 3 at both sides
5w > -26
Divide 5 at both sides
w > -26/5