Question 1142063
at the end of the 7th month, you have 503.


at the end of the 10th month, you have 545.


if you look at this as a straight line equation, the equqtion for that is y = mx + b.


m is the slope and b is the y-intercept.


your slope is the change in y divided by the corresponding change in x.


your change in y would be (545 - 503) = 42


your corresponding change in x would be (10 - 7) = 3


your slope is 42 / 3 = 14.


your equation becomes y = 14 * x + b


your y-intercept is the value of y when x = 0.


to find that, you take any point on the line and replace x and y with that and solve for b.


one point on your line will be (7,503).


7 is equal to x and 503 is equal to y.


y = 14 * x + b becomes 503 = 14 * 7 + b


solve for b to get b = 503 - 14 * 7 = 503 - 98 = 405


your equation becomes y = 14 * x + 405


your y-intercept is 405.


this is the value of y when x is equal to 0.


when x is 7, you get y = 14 * x + 405 becomes y = 14 * 7 + 405 which becomes y = 98 + 405 which becomes y = 503.


when x is 10, you get y = 14 * x + 405 becomes y = 14 * 10 + 405 which becomes y = 140 + 405 which becomes y = 545.


that equation can be graphed.


the graph looks like this.


<img src = "http://theo.x10hosting.com/2019/061001.jpg" alt = "$$$" >


the above equation assumes straight line growth.


for each increase of 1 unit in the value of x, the value of y is increased by 14 units.


when dealing with x and y, the equation is y = 14 * x + 405.


if you replace y with s (savings), and x with m (for months), the equation becomes:


s = 14 * m + 405.


that tells you that, for every increase of 1 in the number of months, the value of your savings is increased by an average of 14.