The property displayed here is the distributive property.
If you have a variable or unknown number inside or outside of parentheses, you can distribute it to each term and add the terms together, and it will remain true.
Example:
4(x + 5)
After distributing, it'll look like this:
4x + 20
First you have to subtract 1350-1000 to get 350. Then you have to make 350/1000 into a percent. First you have to turn it into a decimal. In the fraction 350/1000 can be reduced to 35/100. In decimal form it would be 0.35. In pecentage form it would be 35%. The percentage difference of the student population would be 35%.
2x -1 is the answer I believe