There are two methods to solving this question:
Method 1: Find the equation of the line
Firstly you should calculate the slope, so m = (y2-y1)/(x2-x1)
m = (26-15)/(3-2) = 11
Now use the formula y - y1 = m(x - x1) and either point, let's say (2, 15)
y - 15 = 11(x - 2)
y = 11x - 22 + 15
y = 11x - 7, therefor B is the correct answer
Method 2: substitute the x-values for both points into each equation until you find one where the y-values match those of the points given
A: y = 11x + 7
If x = 2: y = 11*2 + 7 = 29
29 is not equal to 15 therefor A is not the correct answer
B: y = 11x - 7
If x = 2: y = 11*2 - 7 = 15 (this is the same as the point so move on)
If x = 3: y = 11*3 - 7 = 26
This is also right therefor B is the correct answer
In some cases method 2 will be quicker, in some method 1, so really it is a matter of preference