Step-by-step explanation:
perpendicular means to have an angle with the other line of 90°.
the slope (y change / x change) of the original line is 7/6, as the slope is always the factor of x.
the perpendicular slope is turning the original scope upside-down and flips the sign :
-6/7
so, every line with any b
y = -6/7 x + b
is perpendicular to the original line.
the simplest one would be b = 0
y = -6/7 x