Answer:
1.
12 maths book =40 pounds
21 maths book =40×21/12=70 pounds
2.it may be 4.8 or 4.7 sorry question is not clear
3.
perimeter of trapezoid =sum of all side=12+10+19+15=56in
4.
area of trapezoid =1/2 (s1+s2)×h
=1/2 ×12(10+19)=174in²
5.
4²=16
√4=2
so 4² is 8times grater.
