​Combined, there are 187 ​Asians, Africans,​ Europeans, and Americans in a village.

Question

The number of Asians exceeds the number of Africans and Europeans by 81. The difference between the number of Europeans and Americans is 12. If the number of Africans is​ doubled, their population exceeds the number of Europeans and Americans by 30. Determine the number of​ Asians, Africans,​ Europeans, and Americans in this village.

Answer 1

x=y+z+81

y-a=12

2y= z+a+30

x=asians

y=europeans

z=africans

a=americans

in the headline you have 187= x+y+z+a

use substitution, elimination or matrix algebra to solve for each

some calculators will do matrix algebra for you

off hand, I get

x=99 Asians

y= 39 1/3 Europeans

z= 21 1/3 Africans

a = 27 1/3 Americans

which sum to 187. Looks correct.

Unless you require an integer solution

then there is no solution