General solution. Equation of a line passing tru point (a,b) and (c,d):
Solve for y. The order of a,b,c,d is important.
-O
"Something like Y= 3X" would pass through (0,0). It would be better to use the more general y= mx+ b which works for every non-vertical line. Since the line passes through (1, 4), x= 1, y= 4 satisfy the equation: 4= m(1)+ b or m+ b= 4. Since the line passes through (2, 3), x= 2, y= 3 satisfy the equation: 3= m(2)+ b or 2m+ b= 3. You can solve those two equations for m and b and so get the equation.