m=y-b/x-t for y
Add b/x + t to each side:
m + b/x + t = y - b/x - t + b/x + t
Cancel b/x terms and t terms on the right side to get:
y = m + b/x + t
Add b/x + t to each side:
m + b/x + t = y - b/x - t + b/x + t
Cancel b/x terms and t terms on the right side to get:
y = m + b/x + t