The first thing we are going to do for this case is to define the following variable: x = number of trees. We then have that the equation that represents the problem is given by: y = 50 (x-1) + 20 Rewriting: y = 50x - 50 + 20 y = 50x - 30 Substituting for y = 390 we have: 390 = 50x - 30 We clear x: x = (390 + 30) / (50) x = 8.4 nearest whole integer x = 8 Answer: will be planted along one block about 8 trees.
The first one is 100 because it is closer to 100 than to 200. The second one is 700 because 690 is 10 away from 700. And the third one is 100 because it is only 15 away from 100.