If the equation is in the form of y = mx + C, where m and C are real numbers, the slope (which means gradient) of the line is the coefficient of x (I.e. the number to the left of x in simple language), which is m.
In this case, m = 54 and C = -13pie. Both are real numbers, which means that this equation satisfies the form of y = mx + C
m is the coefficient of x, which is 54. 54 is the gradient of this line, which means that for every 54 y-axis units the line increases, the line increases 1 x-axis unit.
Hope this helps! :)
