Answer:

The methods are alike because they are all looking at the equation y = 140 + 50x.

Each will give the solution by finding the month where y is first equal to or greater than $1000.  This occurs at the end of 18 months. 

The equation can be used to find the correct solution.

Knowing that y = 1000, inserting this into the equation and solving it results in x = 17.2. 

Because Janet is putting the money in savings on a monthly basis, she will have $1000, or exactly $1040 at the end of the 18^th month. 

The table is extended for an amount more than $1000 and shows the answer is 18 months. 

The graph shows it takes 18 months to save over $1000.  Seventeen months is less than $1000.