Http://mathsfirst.massey.ac.nz/Algebra/SystemsofLinEq/EMeth.htm this website explains it well
Answer: 140
Step-by-step explanation: 25x20=500
32x20=640
640-500= 140!!
51 ft is the answer
Explanation
The hight of the man divided by the hight of school ( which is unknown )
Equal
The length of the shadow of the man divided by the shadow of the school
Cross multiplication and find the value of unknown x which is 51... and ya