Question 254169
First multiply 2 by (a-8) to give 2a-16. Do the same for 5 and (a+10).

This gives 2a-16+7=5a+10-3a-19

Take 3a away from 5a to give 2a and take 19 away from 10 to give -9. Also add 7 to -16 to give -9.

{{{2a-9=2a-9}}}
 We know this must be true, for all real values of a!