the difference between a proper fraction and an improper fraction is an improper fraction is a fraction that is bigger then the denominator for example 3/4 is a fraction and 7/4 is an improper fraction
Set up the equation as follows:

150x represents the dog's speed, 100x represents the squirrel's speed, and 200 represents the distance the squirrel has on the dog. x is the amount of minutes that elapse.
Subtract 100x from both sides.

Divide both sides by 50.

It will take the dog 4 minutes to catch up with the squirrel.
Answer:
b because the linear equation for the slope given 1/2 and b= 4
871 is closer to 870 than 880, so the answer is 870
These techniques for elimination are preferred for 3rd order systems and higher. They use "Row-Reduction" techniques/pivoting and many subtle math tricks to reduce a matrix to either a solvable form or perhaps provide an inverse of a matrix (A-1)of linear equation AX=b. Solving systems of linear equations (n>2) by elimination is a topic unto itself and is the preferred method. As the system of equations increases, the "condition" of a matrix becomes extremely important. Some of this may sound completely alien to you. Don't worry about these topics until Linear Algebra when systems of linear equations (Rank 'n') become larger than 2.