Explanation:
calm down ! just think logically !
a scaled book ! like a map. that means distances in every direction must have the same scaling (multiplication) factor.
so, now we only need to find out for what answer we have
1.5 × x by 2.0 × x (the same x !)
22.5 by 40 ? 40 = 20×2
but 1.5 × 20 = 30 and not 22.5.
no.
18 by 24 ?
24 = 2 × 12
1.5 × 12 = 18
yes.
19.5 by 20 ?
20 = 2 × 10
1.5 × 10 = 15 and not 19.5.
no.
16 by 24 ?
24 = 2 × 12
1.5 × 12 = 18 and not 16.
no.
so, the answer is 18 cm by 24 cm.