Anumber is being written in scientific notation. the student moves the decimal point to the left 3 places and

a. multiplies by 10-3
b. multiplies by 3
c. multiplies by 10
d. multiplies by 103

i dont get this question either.

If you are moving the decimal point to the left, the exponent is negative. If you move it to the right, the exponent is positive.
There is only one negative exponent here, and it is the first option. 
So:
A number is being written in scientific notation. The student moves the decimal point to the left 3 places and A. multiplies by 10^-3.

The answer to this question is & 17.50