Final answer:
The value of y is determined by substituting the given points and solving for the y-intercept.
Step-by-step explanation:
The line has a slope of 2 and contains the points (1, 3) and (2, y). To find the value of y, we can use the slope-intercept form of a linear equation, which is y = mx + b, where m is the slope and b is the y-intercept.
Since the slope is 2, the equation for the line is y = 2x + b. To find the value of b, we can substitute one of the given points into the equation.
Using the point (1, 3), we have 3 = 2(1) + b. Solving for b, we get b = 1. Therefore, the equation for the line is y = 2x + 1.