Answer:
To find the sum of 30 and 40 by factoring out the greatest common factor, first you need to find the greatest common factor (GCF) of both numbers. The GCF of 30 and 40 is 10. Then, you can divide both numbers by 10 to get 3 and 4 respectively. Finally, add the numbers together to get the sum of 7. Therefore, the sum of 30 and 40 by factoring out the greatest common factor is 7.