Explanation:
let the no. of children be x.
let the no. of adults be y.
x+y= 279 ---(1)
1.25x+7y= 1010 ---(2)
from (1):
x= 279-y ----(3)
sub (3) into (2):
1.25(279-y)+7y= 1010
348.75-1.25y+7y= 1010
5.75y= 661.25
y= 115 ---(4)
sub (4) into (3):
x= 279-115
= 164
therefore, the number of children is 164 and the number of adults is 115.