Explanation:

Take formula (a + b)³ = a³ + 3a²b + 3ab² + b³.  and here assume  Here, a = 6 and b =8.

Step 1 : Take b³ = 8 x 8 x 8 = 512. Take lost digit into the answer last place and remaining value to be add to next step.

i.e Ans :  _ _ _ _ _ 2  and 51 to be add in the next step.

Step 2 : Take 3ab² = 3  x 6 x 64 =  3 x 384 = 1152 and 51 ( from previous step). So 1152 + 51 = 1203. Here Take lost digit into the answer next place and remaining value to be add to next step.

i.e Ans :  _ _ _ _ 3 2  and 120 is to be add in the next step.

 
Step 3 : Take 3a²b =(3  x 36 x 8) + 120=  864 + 120 = 984.  Here Take lost digit into the answer next place and remaining value to be add to next step.

i.e Ans :  _ _ _43 2  and  98 is to be add in the next step.

Step 4 : Take a² =(6 x 6 x 6) + 98=  216 + 98 = 314.  Take this  value into the answer next places.

i.e  Ans : 314432