Help with positive and negative exponent steps and answer

Practice Add or subtract. Write your answer in scientific notation. 1. (3 x 107) + (2.4 X 107) 2. (7.2 X 10-6) + (5.44 X 10-6) 3. (9.2 X 108) - (4 X 108) 4. (7.8 x 10-5) - (4.5 x 10-5) 5. (9.7 X 106) + (6.7 x 105) 6. (8.2 x 102) + (3.41 x 10-1) 7. (1.1 x 105) - (4.3 x 104) 8. (2.4 X 10-1) - (5.5 x 10-2)