The equation of any straight line, called a linear equation, can be written as: y = mx + b, where m is the slope of the line and b is the y-intercept. The y-intercept of this line is the value of y at the point where the line crosses the y axis.
y = -1/2x + 5 is the answer
M = Rise over run meaning you go up 1 and run the other way (left or right) 2