Since the scaled up photo/poster has to be proportional to the original, we can come up with the equation:
![(4)/(6) =(x)/(30)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/2aw605ewl1q8a4re3wqgpcridbnv3f7xae.png)
Now we can solve for x, which is the height of the scaled up poster. We cross multiply the fractions to get 6x=120. Then, we divide 6 on both sides to get x=20.
So, the height of the scaled up photo/poster must be 20 inches.
Hope this helps! Have a great day!