Question 827332
Not right.
The length to width ratio of the drawing is
{{{6/4=3/2=1.5}}}
The drawing's length is 1.5 times its width.
With a width if 20 inches, the same ratio would require a length of 30 inches (1.5 times 20 inches).
{{{6/4=L/20}}} --> {{{6*20/4=L}}} --> {{{L=30}}}
Your poster is not long enough. It is much more "squarish" than the drawing.
You cannot enlarge the drawing so much.
You can only enlarge it enough the fill the length, but will end up with an enlarged drawing narrower than the 20 inch width of the poster.
The width to length ratio of your drawing (before and after enlarging) is
{{{width/"24 inch"=4/6}}} --> {{{width=4*(24inch)/6}}} --> {{{highlight(width=16inch)}}} .
Your enlarged drawing will measure 16 inches by 24 inches.