Plugging in the given point to see which equation is true is not easy on this one, since both values have weird decimals. The answer choices are also likely written so that more than one is true for that point, so try to find another point on the line. The x-intercept of a line is where the line crosses the x-axis. At that point, the value of y is 0. Therefore, (2, 0) is also a point on the line. Plug this point into the answers, since it is easier to calculate. If it works in more than one equation, plugging in the ugly point will determine the correct answer, which must work for both points work. Plug point (2, 0) into (A) to get 0 + 5.9 = 2.5(2). Solve both sides of the equation to get 5.9 = 5. Eliminate (A). Plug (2, 0) into (B) to get 4(0) + 12(2) = 29.1. Solve both sides of the equation to get 4 + 24 = 29.1, or 28 = 29.1. Eliminate (B). Plug (2, 0) into (C) to get 6(0) + 27.15 = 12(2). Solve both sides of the equation to get 0 + 27.15 = 24. Since this is clearly not a true statement, eliminate (C). Plug (2, 0) into (D) to get 10(0) – 13(2) = -26. Solve both sides of the equation to get -26 = -26. Since (D) is the only answer for which the point (2, 0) works, the correct answer is (D).

In a real-world scenario, the slope of a line represents a unit rate and the y-intercept represents a flat fee or a starting amount. Getting to the Answer: The cost of one linear foot is the same as the unit rate (the cost per linear foot), which is represented by the slope of the line. Use the grid-lines and the axis labels to count the rise and the run from the y-intercept of the line (0, 150) to the next point that hits an intersection of two grid-lines. Pay careful attention to how the grid-lines are marked (by 5s on the x-axis and by 25s on the y-axis). The line rises 75 units and runs 5 units, so the slope is ​\( \frac{75}{5}=15 \)​dollars per linear foot of fence. Note that you could also use the slope formula and two points from the graph to find the unit rate.

When a quadratic equation is written in vertex form, y = a(x – h)2 + k, the vertex is (h, k). The vertex of the parabola in the graph is (2, 5); therefore, the equation should look like y = a(x – 2)2 + 5. This means you can eliminate B and C. To choose between (A) and D, consider the value of a. The parabola in the graph opens downward, so a must be negative. This means (A) is correct.