Question 369959
Let M be the number of men, W the number of women, C the number of children
Total number:
1.{{{M+W+C=100}}}
Total receipts:
{{{5M+2W+C/10=100}}}
2.{{{50M+20W+C=1000}}}
You have 3 unknowns but only 2 equations. 
You need another independent equation to be able to solve for your unknowns.