Question

please help me out would appreciate it

Answer 1

We can out the entire left side in terms of a, and then subsitute 5 for a
ab/ (a+b) = c       
b =-1 + a               Substitue (-1 + a) for b
a*(-1+a)/(a+-1+a)=c
(-a+a²)/(2a-1)=c            Subsitute 5 for a
(-5 + 25)/(10-1) = c
20/9 = c

Answer is A) 20/9