What do you do when a variable does not cancel out while solving systems by elimination?

Which graph has a rate of change of zero

Solve: 25 points find the fifth term of an increasing geometric progression if the first term is equal to 7−3 √5 and each term (starting with the second) is equal to the difference of the term following it and the term preceding it.

What is the slope of (0,32) and (100,212)