Greetings from Brasil...
According to the statement, one figure is scaled in relation to another, so we can apply similarity to polygons.....
So
BIG/small = BIG/small
or
small/BIG = small/BIG
27/X = 45/35
OR
35/45 = X/27
27/X = 45/35
45X = 27·35
45X = 945
X = 945/45
X = 21
