First thing you do, is take out the GCF (greatest common factor)
So, what number goes into both 10 and 8?
Obviously, 1. 2 also goes into 10 and 8. Any higher number that would go into both 10 and 8 and give you a whole number? No. So, the GCF is 2
Divide 10 and 8 by 2, and set that in a set of parenthesis with the GCF outide
2(5a+4)
That cannot be factored any further, so that is the answer