Me in number 9 i need the answer and the work

In order to do this problem, you need to follow the exponent rules.

For addition and subtraction, you need to have the same power to add or subtract.

For multiplication and division, you just need to add or subtract the power.

A. 8.6 × 3.2 = 27.52 and then with the powers so it's 10⁷ 
   27.52 × 10⁷ is the same thing as 2.752 × 10⁸ so it cant be choice a
B.  1.870 x 10⁷ + 2.565 x 10⁸ you need the powers to be the same so the change one to make the other one the same so it would be 0.1870 x 10⁸ + 2.565 x 10⁸ which equals to 2.752 x 10⁸ so b cant be it either
C. 6.88 x 10¹¹ ÷ 2.5 x 10³ you just divide 6.88/2.5 = 2.752 and then subtract the exponents so it's 2.752 x 10⁸ c cant be it either
D. 7.887 x 10¹² -- 5.135 x 10⁴ that already doesn't look right because if you just subtract it directly, it's 2.752 and the two powers are completely off

The correct wrong answer is D

Hopes this helps!