Question 231278
Hello, 
First let's distribute so it looks like this: 

         5a^3(8a) - 5a^3(6a)   (Note: When I put ^3 it means to the third power.)

Now, we'll multiply each one out. 

             40a^4 -30a^4

Since these are like terms we can subtract them. 

             Answer is 10a^4

There is another way and maybe shorter for you which is to do the calulation inside the parenthesis like this. 

                         8a - 6a = 2a

Then just multiply  5a^3(2a) = 10a^4


RJ Toftness
www.math-unlock.com