Let the weight of A, B and C be p, q and r

According to the problem statement

⇒ (p + q + r)/3 = 49

⇒ p + q + r = 147      ----(1)

Now given that average weight of A and B is 35 kg

⇒ (p + q)/2 = 35

⇒ p + q = 70 ----(2)

Now, (1) – (2)

⇒ r = 147 – 70 = 77      ----(3)

Now given that average weight of B and C is 62 kg

⇒ (q + r)/2 = 62

⇒ q + r = 124 Using (3)

⇒ q = 124 – 77 = 47 years

∴ the weight of B is 47 years

Let ages of A, B and C are A, B and  C respectively.

Then, Average age of A, B and C :                       (A+B+C)/3 =49

This gives  A+B+C =49×3                                            A+B+C=147............EQ.1

Now given that average of A and B is 35 i.e. (A+B)/2= 35 

This gives A+B= 35×2                                                       =70 .................EQ.2

Also given that average of B and C is 62 i.e. (B+C)/2=62

This gives B+C=62×2                                                         =124..................EQ.3

now adding EQ.1 and EQ.2 ;

We get, A+2B+C=194 

              A+C =194-B

putting value of A+C into EQ.1:

             194-2B+B=147

                 B=47

Hence, the age of B is 47 Kg.